calculus
posted by calculus on .
if y=cosx.sinx find dy/dx

just use the product rule
If y = fg, then
y' = f'g + fg'
So,
dy.dx = sinx.sinx + cosx.cosx
= cos^2x  sin^2x
= cos2x
Or, you could have noticed that
y = 1/2 sin2x, so
y' = cos2x