Here's the question you clicked on:
chikaa
integral of cos(3x-5)^2
use double angles rules
cos2x=2cosx-1 .. did you get it ?
and what about the cos^2
Recall the double angle identity for cosine. \[\cos(2 \alpha )=\cos^2(\alpha)-\sin^2(\alpha)=\cos^2(\alpha)-(1-\cos^2(\alpha))\] \[\cos(2 \alpha)=\cos^2(\alpha)-1+\cos^2(\alpha)\] \[\cos(2 \alpha)=2 \cos^2(\alpha)-1\] Solve this equation for cos^2(alpha): \[\cos^2(\alpha)=\frac{1}{2}(1+\cos(2 \alpha))\]
Thank you Amrmagdy and Myininaya :D