Question

Prove that cos3A=sin2A​

Answer 1

Cos3A= Sin2A ........ (i)

Cos3A= Cos (90-2A)

3A= 90-2A

5A= 90

A= 18

from (i)

Cos(3×18) = Sin (2×18)

Cos54= Sin36

0.5877= 0.5877 proved .

Explanation:

Answer 2

Explanation:

`Cos3A= Sin2A ........ (i)\\\\Cos3A= Cos (90-2A)\\\\3A= 90-2A\\\\5A= 90\\\\A= 18\\\\`

Now,

Putting the value of A to find the value,

`From (i)\\Cos(3x18) = Sin (2x18)\\Cos54= Sin36\\0.5877= 0.5877 \\LHS=RHSProved .`