Hello,
Can someone please tell me how to add trig functions?
for example, what do you add cos2x? is it cosx+cosx = cos2x?
Using the identity
$\displaystyle \cos(a + b) = \cos a \cos b - \sin a \sin b$,
we have
$\displaystyle \cos(2x) = \cos(x + x) = \cos^2x - \sin^2x$.
Then, using the identity
$\displaystyle \sin^2x + \cos^2x = 1$
we have
$\displaystyle \cos(2x) = 2 \cos^2x - 1 = 1 - 2\sin^2x$