Triangles - Math
Card 1 of 880
Acute angles x and y are inside a right triangle. If x is four less than one third of 21, what is y?
Acute angles x and y are inside a right triangle. If x is four less than one third of 21, what is y?
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We know that the sum of all the angles must be 180 and we already know one angle is 90, leaving the sum of x and y to be 90.
Solve for x to find y.
One third of 21 is 7. Four less than 7 is 3. So if angle x is 3 then that leaves 87 for angle y.
We know that the sum of all the angles must be 180 and we already know one angle is 90, leaving the sum of x and y to be 90.
Solve for x to find y.
One third of 21 is 7. Four less than 7 is 3. So if angle x is 3 then that leaves 87 for angle y.
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If a right triangle has one leg with a length of 4 and a hypotenuse with a length of 8, what is the measure of the angle between the hypotenuse and its other leg?
If a right triangle has one leg with a length of 4 and a hypotenuse with a length of 8, what is the measure of the angle between the hypotenuse and its other leg?
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The first thing to notice is that this is a 30o:60o:90o triangle. If you draw a diagram, it is easier to see that the angle that is asked for corresponds to the side with a length of 4. This will be the smallest angle. The correct answer is 30.
The first thing to notice is that this is a 30o:60o:90o triangle. If you draw a diagram, it is easier to see that the angle that is asked for corresponds to the side with a length of 4. This will be the smallest angle. The correct answer is 30.
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In the figure above, what is the positive difference, in degrees, between the measures of angle ACB and angle CBD?
In the figure above, what is the positive difference, in degrees, between the measures of angle ACB and angle CBD?
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In the figure above, angle ADB is a right angle. Because side AC is a straight line, angle CDB must also be a right angle.
Let’s examine triangle ADB. The sum of the measures of the three angles must be 180 degrees, and we know that angle ADB must be 90 degrees, since it is a right angle. We can now set up the following equation.
x + y + 90 = 180
Subtract 90 from both sides.
x + y = 90
Next, we will look at triangle CDB. We know that angle CDB is also 90 degrees, so we will write the following equation:
y – 10 + 2_x_ – 20 + 90 = 180
y + 2_x_ + 60 = 180
Subtract 60 from both sides.
y + 2_x_ = 120
We have a system of equations consisting of x + y = 90 and y + 2_x_ = 120. We can solve this system by solving one equation in terms of x and then substituting this value into the second equation. Let’s solve for y in the equation x + y = 90.
x + y = 90
Subtract x from both sides.
y = 90 – x
Next, we can substitute 90 – x into the equation y + 2_x_ = 120.
(90 – x) + 2_x_ = 120
90 + x = 120
x = 120 – 90 = 30
x = 30
Since y = 90 – x, y = 90 – 30 = 60.
The question ultimately asks us to find the positive difference between the measures of ACB and CBD. The measure of ACB = 2_x_ – 20 = 2(30) – 20 = 40 degrees. The measure of CBD = y – 10 = 60 – 10 = 50 degrees. The positive difference between 50 degrees and 40 degrees is 10.
The answer is 10.
In the figure above, angle ADB is a right angle. Because side AC is a straight line, angle CDB must also be a right angle.
Let’s examine triangle ADB. The sum of the measures of the three angles must be 180 degrees, and we know that angle ADB must be 90 degrees, since it is a right angle. We can now set up the following equation.
x + y + 90 = 180
Subtract 90 from both sides.
x + y = 90
Next, we will look at triangle CDB. We know that angle CDB is also 90 degrees, so we will write the following equation:
y – 10 + 2_x_ – 20 + 90 = 180
y + 2_x_ + 60 = 180
Subtract 60 from both sides.
y + 2_x_ = 120
We have a system of equations consisting of x + y = 90 and y + 2_x_ = 120. We can solve this system by solving one equation in terms of x and then substituting this value into the second equation. Let’s solve for y in the equation x + y = 90.
x + y = 90
Subtract x from both sides.
y = 90 – x
Next, we can substitute 90 – x into the equation y + 2_x_ = 120.
(90 – x) + 2_x_ = 120
90 + x = 120
x = 120 – 90 = 30
x = 30
Since y = 90 – x, y = 90 – 30 = 60.
The question ultimately asks us to find the positive difference between the measures of ACB and CBD. The measure of ACB = 2_x_ – 20 = 2(30) – 20 = 40 degrees. The measure of CBD = y – 10 = 60 – 10 = 50 degrees. The positive difference between 50 degrees and 40 degrees is 10.
The answer is 10.
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Which of the following sets of line-segment lengths can form a triangle?
Which of the following sets of line-segment lengths can form a triangle?
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In any given triangle, the sum of any two sides is greater than the third. The incorrect answers have the sum of two sides equal to the third.
In any given triangle, the sum of any two sides is greater than the third. The incorrect answers have the sum of two sides equal to the third.
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In right
,
and
.
What is the value of
?
In right ,
and
.
What is the value of ?
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There are 180 degrees in every triangle. Since this triangle is a right triangle, one of the angles measures 90 degrees.
Therefore,
.


There are 180 degrees in every triangle. Since this triangle is a right triangle, one of the angles measures 90 degrees.
Therefore, .
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Points A and B lie on a circle centered at Z, where central angle <AZB measures 140°. What is the measure of angle <ZAB?
Points A and B lie on a circle centered at Z, where central angle <AZB measures 140°. What is the measure of angle <ZAB?
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Because line segments ZA and ZB are radii of the circle, they must have the same length. That makes triangle ABZ an isosceles triangle, with <ZAB and <ZBA having the same measure. Because the three angles of a triangle must sum to 180°, you can express this in the equation:
140 + 2x = 180 --> 2x = 40 --> x = 20
Because line segments ZA and ZB are radii of the circle, they must have the same length. That makes triangle ABZ an isosceles triangle, with <ZAB and <ZBA having the same measure. Because the three angles of a triangle must sum to 180°, you can express this in the equation:
140 + 2x = 180 --> 2x = 40 --> x = 20
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In triangle ABC, Angle A = x degrees, Angle B = 2x degrees, and Angle C = 3x+30 degrees. How many degrees is Angle B?

In triangle ABC, Angle A = x degrees, Angle B = 2x degrees, and Angle C = 3x+30 degrees. How many degrees is Angle B?
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Because the interior angles of a triangle add up to 180°, we can create an equation using the variables given in the problem: x+2x+(3x+30)=180. This simplifies to 6X+30=180. When we subtract 30 from both sides, we get 6x=150. Then, when we divide both sides by 6, we get x=25. Because Angle B=2x degrees, we multiply 25 times 2. Thus, Angle B is equal to 50°. If you got an answer of 25, you may have forgotten to multiply by 2. If you got 105, you may have found Angle C instead of Angle B.
Because the interior angles of a triangle add up to 180°, we can create an equation using the variables given in the problem: x+2x+(3x+30)=180. This simplifies to 6X+30=180. When we subtract 30 from both sides, we get 6x=150. Then, when we divide both sides by 6, we get x=25. Because Angle B=2x degrees, we multiply 25 times 2. Thus, Angle B is equal to 50°. If you got an answer of 25, you may have forgotten to multiply by 2. If you got 105, you may have found Angle C instead of Angle B.
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Triangle FGH has equal lengths for FG and GH; what is the measure of ∠F, if ∠G measures 40 degrees?
Triangle FGH has equal lengths for FG and GH; what is the measure of ∠F, if ∠G measures 40 degrees?
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It's good to draw a diagram for this; we know that it's an isosceles triangle; remember that the angles of a triangle total 180 degrees.
Angle G for this triangle is the one angle that doesn't correspond to an equal side of the isosceles triangle (opposite side to the angle), so that means ∠F = ∠H, and that ∠F + ∠H + 40 = 180,
By substitution we find that ∠F * 2 = 140 and angle F = 70 degrees.
It's good to draw a diagram for this; we know that it's an isosceles triangle; remember that the angles of a triangle total 180 degrees.
Angle G for this triangle is the one angle that doesn't correspond to an equal side of the isosceles triangle (opposite side to the angle), so that means ∠F = ∠H, and that ∠F + ∠H + 40 = 180,
By substitution we find that ∠F * 2 = 140 and angle F = 70 degrees.
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The vertex angle of an isosceles triangle is
. What is the base angle?
The vertex angle of an isosceles triangle is . What is the base angle?
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An isosceles triangle has two congruent base angles and one vertex angle. Each triangle contains
. Let
= base angle, so the equation becomes
. Solving for
gives 
An isosceles triangle has two congruent base angles and one vertex angle. Each triangle contains . Let
= base angle, so the equation becomes
. Solving for
gives
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In an isosceles triangle the base angle is five less than twice the vertex angle. What is the sum of the vertex angle and the base angle?
In an isosceles triangle the base angle is five less than twice the vertex angle. What is the sum of the vertex angle and the base angle?
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Every triangle has 180 degrees. An isosceles triangle has one vertex angle and two congruent base angles.
Let
= the vertex angle
and
= base angle
So the equation to solve becomes

or

Thus the vertex angle is 38 and the base angle is 71 and their sum is 109.
Every triangle has 180 degrees. An isosceles triangle has one vertex angle and two congruent base angles.
Let = the vertex angle
and = base angle
So the equation to solve becomes
or
Thus the vertex angle is 38 and the base angle is 71 and their sum is 109.
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An isosceles triangle has a base angle that is six more than three times the vertex angle. What is the base angle?
An isosceles triangle has a base angle that is six more than three times the vertex angle. What is the base angle?
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Every triangle has 180 degrees. An isosceles triangle has one vertex angle and two congruent base angles.
Let
= vertex angle and
= base angle.
Then the equation to solve becomes

or
.
Solving for
gives a vertex angle of 24 degrees and a base angle of 78 degrees.
Every triangle has 180 degrees. An isosceles triangle has one vertex angle and two congruent base angles.
Let = vertex angle and
= base angle.
Then the equation to solve becomes
or
.
Solving for gives a vertex angle of 24 degrees and a base angle of 78 degrees.
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The base angle of an isosceles triangle is thirteen more than three times the vertex angle. What is the difference between the vertex angle and the base angle?
The base angle of an isosceles triangle is thirteen more than three times the vertex angle. What is the difference between the vertex angle and the base angle?
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Every triangle has
. An isosceles triangle has one vertex ange, and two congruent base angles.
Let
be the vertex angle and
be the base angle.
The equation to solve becomes
, since the base angle occurs twice.



Now we can solve for the vertex angle.

The difference between the vertex angle and the base angle is
.
Every triangle has . An isosceles triangle has one vertex ange, and two congruent base angles.
Let be the vertex angle and
be the base angle.
The equation to solve becomes , since the base angle occurs twice.
Now we can solve for the vertex angle.
The difference between the vertex angle and the base angle is .
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Sides
and
in this triangle are equal. What is the measure of
?

Sides and
in this triangle are equal. What is the measure of
?

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This triangle has an angle of
. We also know it has another angle of
at
because the two sides are equal. Adding those two angles together gives us
total. Since a triangle has
total, we subtract 130 from 180 and get 50.
This triangle has an angle of . We also know it has another angle of
at
because the two sides are equal. Adding those two angles together gives us
total. Since a triangle has
total, we subtract 130 from 180 and get 50.
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An isoceles triangle has a base angle five more than twice the vertex angle. What is the difference between the base angle and the vertex angle?
An isoceles triangle has a base angle five more than twice the vertex angle. What is the difference between the base angle and the vertex angle?
Tap to reveal answer
A triangle has 180 degrees. An isoceles triangle has one vertex angle and two congruent base angles.
Let
= vertex angle and
= base angle
So the equation to solve becomes
or 
So the vertex angle is
and the base angle is
so the difference is 
A triangle has 180 degrees. An isoceles triangle has one vertex angle and two congruent base angles.
Let = vertex angle and
= base angle
So the equation to solve becomes
or
So the vertex angle is and the base angle is
so the difference is
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An isosceles triangle has a vertex angle that is twenty degrees more than twice the base angle. What is the sum of the vertex and base angles?
An isosceles triangle has a vertex angle that is twenty degrees more than twice the base angle. What is the sum of the vertex and base angles?
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All triangles contain
degrees. An isosceles triangle has one vertex angle and two congruent base angles.
Let
and
.
So the equation to solve becomes
.
We get
and
, so the sum of the base and vertex angles is
.
All triangles contain degrees. An isosceles triangle has one vertex angle and two congruent base angles.
Let and
.
So the equation to solve becomes .
We get and
, so the sum of the base and vertex angles is
.
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If an isosceles triangle has an angle measuring greater than 100 degrees, and another angle with a measuring
degrees, which of the following is true?
If an isosceles triangle has an angle measuring greater than 100 degrees, and another angle with a measuring degrees, which of the following is true?
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In order for a triangle to be an isosceles triangle, it must contain two equivalent angles and one angle that is different. Given that one angle is greater than 100 degrees:
Thus, the sum of the other two angles must be less than 80 degrees. If an angle is represented by
: 
In order for a triangle to be an isosceles triangle, it must contain two equivalent angles and one angle that is different. Given that one angle is greater than 100 degrees: Thus, the sum of the other two angles must be less than 80 degrees. If an angle is represented by
:
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An isoceles triangle has a base angle that is twice the vertex angle. What is the sum of the base and vertex angles?
An isoceles triangle has a base angle that is twice the vertex angle. What is the sum of the base and vertex angles?
Tap to reveal answer
All triangles have
degrees. An isoceles triangle has one vertex angle and two congruent base angles.
Let
vertex angle and
base angle.
So the equation to solve becomes:
or 
Thus
for the vertex angle and
for the base angle.
The sum of the vertex and one base angle is
.
All triangles have degrees. An isoceles triangle has one vertex angle and two congruent base angles.
Let vertex angle and
base angle.
So the equation to solve becomes:
or
Thus for the vertex angle and
for the base angle.
The sum of the vertex and one base angle is .
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An isoceles triangle has a vertex angle that is
degrees more than twice the base angle. What is the vertex angle?
An isoceles triangle has a vertex angle that is degrees more than twice the base angle. What is the vertex angle?
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Every triangle has
degrees. An isoceles triangle has one vertex angle and two congruent base angles.
Let
base angle and
vertex angle.
So the equation to solve becomes
.


Thus the base angles are
and the vertex angle is
.
Every triangle has degrees. An isoceles triangle has one vertex angle and two congruent base angles.
Let base angle and
vertex angle.
So the equation to solve becomes .
Thus the base angles are and the vertex angle is
.
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An isoceles triangle has a base angle that is
degrees less than three times the vertex angle. What is the product of the vertex angle and the base angle?
An isoceles triangle has a base angle that is degrees less than three times the vertex angle. What is the product of the vertex angle and the base angle?
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Every triangle has 180 degrees. An isoceles triangle has one vertex angle and two congruent base angles.
Let
vertex angle and
base angle.
Then the equation to solve becomes:
, or
.
Then the vertex angle is
, the base angle is
, and the product is
.
Every triangle has 180 degrees. An isoceles triangle has one vertex angle and two congruent base angles.
Let vertex angle and
base angle.
Then the equation to solve becomes:
, or
.
Then the vertex angle is , the base angle is
, and the product is
.
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An isoceles triangle has a base angle that is twice the vertex angle. What is the sum of one base angle and the vertex angle?
An isoceles triangle has a base angle that is twice the vertex angle. What is the sum of one base angle and the vertex angle?
Tap to reveal answer
Every triangle contains
degrees. An isoceles triangle has two congruent base angles and one vertex angle.
Let
the vertex angle and
the base angle
So the equation to solve becomes
or
and dividing by
gives
for the vertex angle and
for the base angle, so the sum is 
Every triangle contains degrees. An isoceles triangle has two congruent base angles and one vertex angle.
Let the vertex angle and
the base angle
So the equation to solve becomes or
and dividing by
gives
for the vertex angle and
for the base angle, so the sum is
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