Question

Cos alpha+ cos 3alpha +cos 5alpha+ cos 7alpha+ cos 9alpha =sin 10alpha/2sin alpha

Answer 1

Answer:

Correct option is

C

1

cos9α=sinα

⇒cos9α=cos(90°−α)

⇒9α=90°−α

⇒10α=90°

⇒α=9°

∴tan5α=tan45°=1

Hence, the answer is 1.