Third Angles Theorem

Triangle Sum Theorem

Make sure you have a calculator!

Triangle Sum Theorem- using what you just learned, answer the following questions

Reminder: the angles of a triangle add up to 180 degrees!

Multiple Choice

A triangle has one angle that measure 45° and one that measures 60°. What is the measure of the third angle?

• 135°

• 75°

• 120°

• 105°

Multiple Choice

Will the following three angles for a triangle?

30°, 60°, 90°

• yes

• no

Multiple Choice

Find the measure of the missing angle.

• 30^o

• 110^o

• 150^o

• 40^o

Multiple Choice

A student is trying to construct triangles using four different sets of angles. The angles in each set are given below. Which set will form a triangle?

• 45°, 65°, 70°

• 150°, 110°, 100°

• 50°, 50°, 50°

• 90°, 90°, 90°

Multiple Choice

Find the measure of the indicated angle. 

• 26
• 36
• 85
• 144

Multiple Choice

If 2 of the angles of a triangle are 30 and 70 degrees, the third angle measures...

• 80
• 100
• 60
• 90

Multiple Choice

Angles that are exactly 90 degrees are called _____ ______.

• tight angles
• acute angles
• obtuse angles
• right angles

Multiple Choice

Find the measure of the missing angle.

• 90^o
• 10⁰
• 130^o
• 50^o

Multiple Choice

What is the third angle of a triangle whose 1st angle is 79 and the 2nd angle is 43?

• 43
• 58
• 72
• 101

Multiple Choice

The Triangle Sum Theorem states that the sum of all angles in a triangle is ______.

• 45°

• 90°

• 180°

• 360°

Multiple Choice

Find the measure of the angle indicated. 

• 139°
• 66°
• 138°
• 116°

Multiple Choice

Solve for x. (Hint: 70 + 60 + 8x + 2 = 180; combine like terms and solve for x)

• 16

• 11

• 50

• 6