sin4xsin3x - sin2xsin5x + sin4xsin7x / cos2xcos3x - cos2xcox7x + cosxcos10x
=( 1/2[cos7x - cosx - cos7x + cos3x + cos11x - cos3x] ) / (1/2[cos5x + cosx - cos9x - cos5x + cos11x +cos9x])
= cos11x - cosx / cos11x + cosx = -2sin6xsin5x/2cos6xcos5x
=-tan6xtan5x
