Angle Addition Postulate
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�.
Examples of Angle Addition Postulate

According to angle addition postulate, m?DAC + m?CAB = m?DAB. So, m?DAB = 35� + 30� = 65�.
Video Examples: Angle Addition Postulate  Geometry Help
Solved Example Clockple on Angle Addition Postulate
Ques:
Find m?CAB. [Given ?DAB = 64� and ?DAC = 53�.]
Choices:
A. 28B. 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.]
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