cos20cos40cos60cos80=?
Answers
Answered by
50
hi zoom it and note it ......thanks
Attachments:

Answered by
28
Hi,
We know that ,
__________________________
Cos x cos ( 60 - x ) cos ( 60 + x )
= 1/4 cos 3x
__________________________
Given ,
Cos 20 Cos40 Cos 60 Cos 80
= Cos 20 Cos 40 Cos 80 Cos 60
=[ Cos 20 Cos ( 60 - 20 ) Cos ( 60 + 20 )] Cos 60
= 1/4 × Cos ( 3 × 20 ) Cos 60
= 1/4 Cos 60 × Cos 60
= 1/4 × 1/2 × 1/2
= 1/ 16
I hope this helps you.
:)
We know that ,
__________________________
Cos x cos ( 60 - x ) cos ( 60 + x )
= 1/4 cos 3x
__________________________
Given ,
Cos 20 Cos40 Cos 60 Cos 80
= Cos 20 Cos 40 Cos 80 Cos 60
=[ Cos 20 Cos ( 60 - 20 ) Cos ( 60 + 20 )] Cos 60
= 1/4 × Cos ( 3 × 20 ) Cos 60
= 1/4 Cos 60 × Cos 60
= 1/4 × 1/2 × 1/2
= 1/ 16
I hope this helps you.
:)
Similar questions
English,
10 months ago
English,
10 months ago
Math,
10 months ago
India Languages,
1 year ago
English,
1 year ago