##int cos^2/sin x d x=l n(tan(x/2))+cos x+C##

##int cos^2/sin x d x= ?##

##cos^2 x=1-sin^2x##

##int(1-sin^2 x)/(sin x) d x=int (1/sin x-sin x)d x ##

##int cos^2/sin x d x=int (d x)/sin x- int sin x d x##

##int cos^2/sin x d x=l n(tan(x/2))+cos x+C##