while differentiating why do we convert sin2wt(sin square omega t) to 1-coswt

u need not convert sin 2 wt while differentiating
but u need to convert while integrating as u don't know the value integral of it.. see the attached file

ya so much

u need not convert sin 2 wt while differentiating
but u need to convert while integrating as u don't know the value integral of it.. see the attached file

thank you so much