cos12°+cos60°+cos84°=cos24°+cos48°
Answers
Answered by
14
It was helpful.......
Attachments:
shubhamkumar1234:
nice solution
Answered by
30
Hi friend,
cos12°+cos60° + cos 84° = cos24°+cos48°
=cos24 - cos 84 + cos 48 - cos 12=cos60
= 2sin 54°× sin30 + 2 sin 30 × sin (-18) = cos 60;
= sin 54 - sin 18 = cos 60
= 2 cos 36 × sin18 = cos 60
= 2×1/4 ( root 5 + 1 ) × 1/4 ( root 5 - 1 ) = 1/2
= 1/2 × ( 5 - 1 ) × 1/4 = 1/2
=1/2 = 1/2
i hope it helps
if it works you mark me as a brainlist.
cos12°+cos60° + cos 84° = cos24°+cos48°
=cos24 - cos 84 + cos 48 - cos 12=cos60
= 2sin 54°× sin30 + 2 sin 30 × sin (-18) = cos 60;
= sin 54 - sin 18 = cos 60
= 2 cos 36 × sin18 = cos 60
= 2×1/4 ( root 5 + 1 ) × 1/4 ( root 5 - 1 ) = 1/2
= 1/2 × ( 5 - 1 ) × 1/4 = 1/2
=1/2 = 1/2
i hope it helps
if it works you mark me as a brainlist.
Similar questions