Question

If a = 30 verify cos 3a = 4 cos cube a - 3cosa

Answer 1

Hi...
dear..here is your answer!!!.......
Given,
a = 30.

Cos3a=. cos3*30°
= cos90°
> = 0
cos3a= 0....>>>
again...,
4 cos cube a - 3cosa= 4*cos^30 - 3cos30
........... = 4(√3/2)^3 - 3*√3/2....
= 4*3√3/8- 3√3/2
........= 3√3/2 - 3√3/2
= 0 ..
...4 cos cube a - 3cosa= 0...

hence....
cos 3a = 4 cos cube a - 3cosa is true.!!!
Hope this helps you!!
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#shubhendu

Answer 2

Answer:

Step-by-step explanation:Given,

a = 30.

Cos3a=. cos3*30°

= cos90°

> = 0

cos3a= 0....>>>

again...,

4 cos cube a - 3cosa= 4*cos^30 - 3cos30

........... = 4(√3/2)^3 - 3*√3/2....

= 4*3√3/8- 3√3/2

........= 3√3/2 - 3√3/2

= 0 ..

...4 cos cube a - 3cosa= 0...

hence....

cos 3a = 4 cos cube a - 3cosa is true.!!!

Hope this helps you!

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