Finding Unknown Angle Measures

Finding Unknown Angle Measurements

What do we already know?

Angle ABC = 40 $\degree$  

What else do we know?

Solve for  $\angle$  CBH
90 $\degree$  - 40 $\degree$  = ?

Where did 90 $\degree$ come from? 

90 $\degree$  is the measure of  $\angle$  ABH which is a right angle.

Complementary Angles

are two angles that add up to 90°

Example from the picture to the right: 40° + 50° = 90°

More

Examples: 45° + 45° = 90°

Example: 82° + 8° = 90°

Multiple Choice

Find the measure of $\angle$  DEG

• 46 $\degree$  

• 36 $\degree$  

• 90 $\degree$  

• 126 $\degree$  

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Multiple Choice

Which pair of angle measurements are complementary?

• 18 $\degree$ 72 $\degree$

• 50 $\degree$ 30 $\degree$

• 25 $\degree$ 75 $\degree$

• 45 $\degree$ 35 $\degree$

Multiple Choice

What is the measurement of angle a?

• 30 $\degree$

• 25 $\degree$

• 90 $\degree$

• 60 $\degree$

Supplementary Angles

Two angles that add up to 180°

Examples: 120° + 60°= 180°

Example: 84° + 96°= 180°

What is the measure of angle a if angle b measures 68 $\degree$  ?

Notice that a and b together equal a straight line.

Multiple Choice

 Find the measure of $\angle$  PQS

• 34 $\degree$  

• 56 $\degree$  

• 146 $\degree$  

• 180 $\degree$  

Multiple Choice

Angle MNP and Angle PNO have a combined measure of 180 $\degree$ 
The measure of  $\angle$  MNP is 87 $\degree$  

What is the measure of  $\angle$  PNO in degrees?
The measure of  $\angle$  PNO is ____________ degrees.

• 87 $\degree$  

• 3 $\degree$  

• 93 $\degree$  

• 103 $\degree$  

Multiple Choice

Angle ABC is divided into 2 smaller angles by a ray. One of the smaller angles formed is an obtuse angle and the other is an acute angle. Which of the following could NOT be the measure of angle ABC?

• 79 $\degree$

• 93 $\degree$

• 107 $\degree$

• 119 $\degree$

Angles on a Straight Line Add Up to 180

What does angle b equal?

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Multiple Choice

What is the measure of angle KGH 

if angle EGK measures 59 $\degree$ ?

The measurement of angle KGH is ______ degrees.

• 59 $\degree$  

• 31 $\degree$  

• 180 $\degree$  

• 121 $\degree$  

Multiple Choice

Angle AED and angle DEC are adjacent right angles. Together, they form angle AEC. What type of angle is angle AEC?

• acute

• obtuse

• right

• straight