Differentiate the following functions with respect to x :
sin x−x cos xx sin x+cos x
We have,
ddx(sin x−x cos xx sin x+cos x)
Apply quotient rule, we get
=(x sin x+cos x)ddx(sin x−x cos x)−(sin x−x cos x)ddx(x sin x+cos x)(x sin x+cos x)2
=(x sin x+cos x){cos x−(dxdxcos x+cos xdxdx)}−(sin x−x cos x)(dxdxsin x+sin xdxdx)+ddxcos x(x sin x+cos x)2
=(x sin x+cos x)(cos x+x sin x−cos x)−(sin x−x cos x)(x cos x+sin x−sin x)(x sin x+cos x)2
=(x sin x+cos x)x sin x−(sin x−x cos x)×cos x(x sin x+cos x)2=x2sin2x+x sin x cos x−x sin x cos x+x2cos2x(x sin x+cos x)2
=x2(sin2x+cos2x)(x sin x+cos x)2 (∵ sin2x+cos2=1) =x2x sin x+cos x