Angles of Triangles

Title - Angles of Triangles

These are your NOTES. To earn credit copy each example into your notes. Then answer the questions at the end. You can try more than once if you need to. You will need your marble notebook and a calculator.

Angle Sum of a Triangle

• The sum of the measures of the interior angles of a triangle is 180^o.

• <1 + <2 + <3 = 180

Find the missing angle.

In Δ MAY , if m<M = 72^o and the m<Y = 74^o

Give this a try! The work and answer are on the next slide.

So what is angle A?

• Remember the sum of all three angles is 180.

• m<A = 180 - (72 + 74)

• m<A = 180 - 146

• m<A = 34^o

Here is another example. The measures of the angles of a ΔABC are in the ratio 1:4:5. What are the measures of the angles?

• Let x = angle A

• Then ......4x = angle B and 5x = angle C

• Now we can make a equation! x + 4x + 5x = 180

• 10x = 180

• x = 18

If x = we now can find all the angles!

• m<A = x = 18

• m<B = 4x = 4(18) = 72

• m<C = 5x = 5(18) = 90

• The measures of the angles are 18^o, 72^o, and 90^o

Multiple Choice

Find the missing angle x.

• 145^o

• 90^o

• 35⁰

• 180^o

Please copy this into your notes!

Finding x

Remember the sum of the remote interior angles equals the exterior angle.

So........

63 + 86 = x

149 ^o = x

Finding x when it is a interior angle!

• The sum of the remote interior angles equals the exterior angle.

• x + 40 = 100

• -40 from both sides

• x = 60^o

LETS DO THIS!

Multiple Choice

In a triangle, how many total degrees are there?

• 100%
• 180 degrees
• it varies
• 360 degrees

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 missing angle.

• 90^o

• 10⁰

• 130^o

• 50^o

Multiple Choice

Find the measure of the indicated angle.

• 95

• 85

• 35

• 45

Multiple Choice

The sum of the remote interior angles equals the exterior angle.

Multiple Choice

Which of the following terms best describes Angle d?

• Remote interior angle

• Corresponding angle

• Exterior angle

• Interior angle

Multiple Choice

Find the measure of angle x. Be careful! They did NOT give you two remote interior angles.

• 138

• 96

• 93

• 87

Multiple Choice

Find the measure of the missing angles.

• A

• B

• C

• D

Multiple Choice

Hint: Remeber their sum is 180^o.

• 11

• 25

• 35

• 50