## shahzadjalbani 2 years ago Derivative of cos x^2 by abinitio method.......?

I don't know what the abinitio method is, but you can differentiate this by using the chain rule.$\frac {d}{dx} \left[ \cos^2 x \right] = 2 \cos x * \frac {d}{dx} \left[ \cos x \right] = -2 \cos x \sin x = -\sin 2x$