Question

Prove that tan10,tan25,tan45,tan65,tan80=1

Answer 1

Answer:

L.H.S. = tan 10˚ tan 15˚ tan 75˚ tan 80˚

= tan 10˚ tan 15˚ tan (90˚ – 15˚) tan(90˚ – 10˚)

= tan 10˚ tan 15˚ cot 15˚ cot 10˚

1/cot10˚ × 1/cot 15˚ × cot 15˚ × cot 10˚

= 1 = R.H.S.

Hence proved.

(ii) L.H.S. = cos 1˚ cos 2˚ cos 3˚ …..cos 180˚

= cos1˚ cos2˚ cos 3˚ …..cos 89˚ cos 90˚ ….cos 180˚

= cos 1˚ cos 2˚ cos 3˚ ….cos 89˚ × 0 × cos 91˚ ….cos 180˚

= 0 = R.H.S.

Hence proved.

Step-by-step explanation:

plz mark me as a Brainliest