# Thread: Indentity for cos^2a clarification

1. ## Indentity for cos^2a clarification

I have this equation: y(t)=[A+m(t)]cos^2(wt)

I going to use the power reduction identity cos^2a=(1+cos2a)/2

I'm not sure how to handle the coefficient [A+m(t)], is a more general form of the identity: Bcos^2(a)=(B+Bcos2a)/2

So my solution would be?

y(t)=[A+m(t)]/2 + [A+m(t)]cos^2(wt)/2

If someone could clarify this, I would appreciate it, thanks.

2. $\displaystyle y(t)=(A+m(t))\cos^2(wt)$

$\displaystyle \cos^2(wt) = \frac{1+\cos(wt)}{2}$

so $\displaystyle y(t)=(A+m(t))\cos^2(wt) = (A+m(t))\times \frac{1+\cos(wt)}{2}$

$\displaystyle y(t) = \frac{(A+m(t))\times +(A+m(t))\cos(wt)}{2}=\dots$