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’.

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