Question

sin 47° cos 43°+ cos 47° sin 43° = ? 

(a) sin 4°

(b) cos 4°

(c) 1 

(d) 0

Answer 1

Correct answer = (c) 1

We have

(sin 43° cos 47° + cos 43° sin 47°)

= sin 43° cos(90° − 43°) + cos 43° sin(90° − 43°) 

= sin 43° sin 43° + cos 43° cos 43° [∵ cos(90° − θ) = sin θ and sin(90° − θ) = cos θ] 

= sin² 43° + cos² 43°

= 1