1.

sin 47° cos 43°+ cos 47° sin 43° = ? (a) sin 4°(b) cos 4°(c) 1 (d) 0

Answer»

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



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