Question

find the degree measure of an angle which is equal to its supplement.

Answer 1

The degree measure of an angle which is equal to its supplement is ∠90°

Supplementary angle: Two angles which together forms an angle of 180°

Example: if we have 50°, 130° is its supplementary angle.

Since we need an angle which is equal to it supplementary that is only possible for 90°

If we have 90°,its supplementary angle is also 90°, 90°+90°=180°

Answer 2

let the first angle be x and its supplement angle by y

ATQ,

x=y—(1)

and

x+y=180(supplementary angles)
x+x=180(from(1))
2x=180
x=180/2
x=90°

so, the angle is of 90°