ANGLE MEASURES IN TRIANGLES WORKSHEET

About "Angle measures in triangles worksheet"

Angle measures in triangles worksheet :

Worksheet given in this section is much useful to the students who would like to practice problems on finding missing angle measures in triangles. 

Angle measures in triangles worksheet - Problems

Problem 1 :

The measure of one acute angle of a right triangle is two times the measure of the other acute angle. Find the measure of each acute angle. 

Problem 2 :

Find the missing angles in the triangle shown below. 

Problem 3 :

Find the value of x in the diagram shown below. 

Problem 4 : 

Find the missing angles in the triangle shown below. 

Angle measures in triangles worksheet - Problems

Problem 1 :

The measure of one acute angle of a right triangle is two times the measure of the other acute angle. Find the measure of each acute angle. 

Solution : 

Let A, B and C be the vertices of the triangle and right angle is at C. 

Let ∠A = x°, then ∠B = 2x°. The diagram shown below illustrates this. 

By Corollary to the Triangle Sum Theorem, the acute angles of a right triangle are complementary.  

So, we have 

x° + 2x°  =  90°

Simplify.

3x°  =  90°

Divide both sides by 3.

x  =  30

So, m∠A = 30°  and m∠B = 2(30°)  =  60°

Hence, the two acute angles are 30° and 60°. 

Problem 2 :

Find the missing angles in the triangle shown below. 

Solution : 

In the triangle shown above, two sides are congruent. Angles opposite to congruent sides are always congruent. 

So, if one missing angle is assumed to be x°, then the other missing angle also must be x°. Because the two angles are congruent. 

The diagram shown below illustrates this. 

By Triangle Sum Theorem, the sum of the measures of the interior angles of a triangle is 180°. 

So, we have 

x° + x° + 40°  =  180°

Simplify. 

2x + 40  =  180

Subtract 40 from both sides. 

2x  =  140

Divide both sides by 2. 

x  =  70 

Hence, the measure of each missing angle is 70°.

Problem 3 :

Find the value of x in the diagram shown below. 

Solution :

By Exterior Angle Theorem, the measure of an exterior angle of a triangle is equal to the sum of the measures of the two nonadjacent interior angles. 

So, we have 

x° + 65°  =  (2x + 10)°

or 

x + 65  =  2x + 10

Subtract x from both sides. 

65  =  x + 10

Subtract 10 from both sides. 

55  =  x

Hence, the value of x is 55. 

Problem 4 : 

Find the missing angles in the triangle shown below. 

Solution : 

In the triangle shown above, two sides are congruent. Angles opposite to congruent sides are always congruent. 

So, if one missing angle is assumed to be x°, then the other missing angle also must be x°. Because the two angles are congruent. 

The diagram shown below illustrates this. 

In the triangle shown above, one of the angles is right angle. So, it is right triangle.

By Corollary to the Triangle Sum Theorem, the acute angles of a right triangle are complementary.  

So, we have 

x° + x°  =  90°

Simplify. 

2x  =  90

Divide both sides by 2. 

x  =  45

Hence, the measure of each missing angle is 45°.

After having gone through the stuff given above, we hope that the students would have understood, "Angle measures in triangles worksheet". 

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