Here,
#I=intsin^2x/sqrt(1-cosx)dx=int(sin^2x)/sqrt(1-
cosx)xxsqrt(1+cosx)/sqrt(1+cosx)dx#
#I=int(sin^2xsqrt(1+cosx))/sqrt(1-cos^2x)dx#
#=int(sin^2xsqrt(1+cosx))/sinx dx#
#=intsinxsqrt(2cos^2(x/2))dx#
#=int2sin(x/2)cos(x/2)*sqrt2cos(x/2)dx#
#=2sqrt2intcos^2(x/2)sin(x/2) dx#
#=2sqrt2int[cos(x/2)]^2(-1/2sin(x/2))(-2)dx#
#=-4sqrt2int[cos(x/2)]^2d/(dx)(cos(x/2))dx#
#=-4sqrt2[cos(x/2)]^3/3+c#
#=(-4sqrt2)/3cos^3(x/2)+c#