Question

intergrate cos ^2 (3X)

Answer 1

You have to use a power-reduction formula:

\[\cos^{2}x = \frac{ 1+\cos2x }{ 2 }\]So basically, you rewrite your function as:
\[\cos^{2}(3x) = \frac{1+\cos(6x)}{2}\]Then you can integrate like normal :3

Answer 2

if we change it to \[1-\sin ^2 (3X)\]

Answer 3

That doesnt really make things any different. It would still be the same problem, except if you were to do a power-reduction formula with sin, itd be
\[\sin^{2}x = \frac{1-\cos2x}{2}\] Theres no real use of using an identity other than the power-reduction one.

Answer 4

ok thank you :)

Answer 5

mhm : )