Math questions!!!(urgent!!)

1. y= 4csc2x
y' =(css2x)(4csc2x-1)(2csc2xtan2x)
=(4csc2x-1)(2csc22xtan2x)

2. ∫sin5x cos4x dx
=∫sinx(sinxcosx)4dx
=∫sinx(1/2 sin2x)4dx
=1/16∫sinxsin42xdx
=1/16∫sinx[1/2 (1-cos4x)]2 dx
=1/64∫sinx (1-2cos4x+cos24x) dx
=1/64∫sinx [1-2cos4x+1/2(1+cos8x)] dx
=1/64∫sinx [3/2 -2cos4x+1/2cos8x)] dx
=1/64∫(3/2sinx -2cos4xsinx +1/2cos8xsinx)dx
=1/64∫[3/2sinx -(sin5x-sin3x) +1/4(sin9x-sin7x)]dx
=1/64∫(3/2sinx -sin5x+sin3x +1/4sin9x-1/4sin7x)dx
= -3/128 cosx + 1/320 cos5x -1/193 cos3x -1/2304 cos7x -/1792 cos7x+C


3.∫sin9x sin3x dx
=∫1/2(sin12x+sin6x)dx
=1/2∫sin12xdx+1/2∫sin6xdx
=-1/24cos12x-1/12cos6x+C