" 20."(cos x-cos2x)/(1-cos x)

int(cos x-cos2x)/(1-cos x)*dx

Integrate the following: int{(5cos^3x+2sin^3 x)/(2sin^2 x*cos^2 x)+sqrt(1+sin2x)+(1+2sin x)/(cos^2x)+(1-cos2x)/(1+cos 2x)}dx

To prove (cos5x+cos4x)/(1-2cos3x) = -cos2x-cosx

To prove (cos5x+cos4x)/(1-2cos3x)=-cos2x-cos x

Prove that: (cos7x-cos8x)/(1+2cos5x)=cos2x-cos3x

Prove that: (cos7x-cos8x)/(1+2cos5x)=cos2x-cos3x

cos ^(-1) ""((cos x + cos y)/(1+cos x cos y))= 2 tan ^(-1) (tan ""(x)/(2) tan ""(y)/(2))

lim_(x->0)(1-cos x-cos2x+cos x*cos2x)/(x^(4))

Lim_(x->0)(1-cos x-cos2x+cos x cos2x)/(x^(4))