Question

The two angles of a triangle are complementary. The third angle is
(a) 60°
(b) 45°
(c) 36°
(d) 90°

Answer 1

Correct option: (d)
The measure of two angles are complimentary if their sum is 90^o degrees.
Let the two angles be x and y, such that x + y = 90^o .
Let the third angle be z.
Now, we know that the sum of all the angles of a triangle is 180^o​.
x + y + z​ = 180^o
⇒ 90^o + z = 180^o
⇒ z = 180^o $-$ 90^o
= 90^o
​The third angle is 90^o.