In the following Triangle ABC, find measure of exterior ∠ 1:

Example 1: In the following Triangle ABC, find measure of exterior ∠ 1:
Solution 1: As shown in the given example:
∠ C = 55°
∠ A = 80°
∠ A & ∠ C are interior opposite angles to exterior ∠ 1
So, as per Exterior Angle Property of Triangle; we get:
∠ 1 = ∠ A + ∠ C
Put the values of ∠ A & ∠ C from above and we get:
∠ 1 = 55° + 80°
Solve R.H.S and we get:
∠ 1 = 135°
Hence, measure of exterior ∠ 1 = 135°

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