**Definition of Angle Addition Postulate**

- Angle Addition Postulate states that if a point S lies in the interior of ∠PQR, then ∠PQS + ∠SQR = ∠PQR.

**More about Angle Addition Postulate**

- If the sum of the two angles measure up to 90°, then the angles are called to be ‘complementary angles’.
- If the sum of the two angles measure up to 180°, then the angles are called to be ‘supplementary angles’.
- The angles sharing a common side are called as ‘adjacent angles’.

**Example of Angle Addition Postulate**

- According to angle addition postulate,
*m*∠DAC +*m*∠CAB =*m*∠DAB. So,*m*∠DAB = 35° + 30° = 65°.

**Solved Example on Angle Addition Postulate**

Find

m∠CAB. [Given ∠DAB = 64° and ∠DAC = 53°.]

Choices:

A. 28

B. 15

C. 11

D. 117

Correct Answer: C

Solution:

Step 1:m∠DAC +m∠CAB =m∠DAB [Angle Addition Postulate.]

Step 2: ⇒m∠CAB =m∠DAB -m∠DAC

Step 3:⇒m∠CAB = 64 – 53 [Substitute.]

Step 4:m∠CAB = 11 [Add.]

**Related Terms for Angle Addition Postulate**

- Adjacent Angles
- Angle
- Complementary Angles
- Interior
- Sum
- Supplementary Angles