Question

Which of the following statements is true?

a. sin 18° = cos 72°
b. sin 55° = cos 55°
с. sin 72° = cos 18°
d. Bоth a and c.

Answer 1

The answer is d.

Explanation:

As we know, sin x= cos (90°-x)

sin 18° = cos (90°-18°)

= cos 72°.

Similarly, sin 72°= cos (90°-72°)

= cos 18°

But, sin 55°= cos (90°-55°)

= cos 35°