Question

Prove the followings:-

(i) cos20°× cos40°× cos60°× cos80° = 1/16.

(ii) sin10°× sin30°× sin50°× sin70° = 1/16.​

Answer 1

Answer:

(i) cos20°× cos40°× cos60°× cos80° = 1/16.

(ii) sin10°× sin30°× sin50°× sin70° = 1/16.

✌️Hope it will help you.✌️

Answer 2

Answer:

using theorem

costheta ×cos2theta×cos3theta×cos4 theta=1/16

then

they is 20°

it is 1/4×cos^260

=1/4×1/4

hence it is 1/16

ok

similarly

sin10°×sin30×sin50×sin70

as

cos20*cos40*cos60*cos80

then

it is also =1/16

ok

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