using subsitution the answer is wrong, but from what i know, it should work
integral (sinx.cosx)
=integral (u) let u=sinx, du=cosx dx
=1/2u^2 +c
=1/2sin^2x +c
=1/2[1/2(1-cos2x)] +c
=1/4-1/4cos2x +c
but then there's also,
integral (sinx.cosx)
=1/2 integral (sin2x)
=1/2.-1/2cos2x...