cos(x + y) = cosx*cosy - sinx*siny

tg(x + y) = tgx + tgy/ 1 - tgx*tgy

ctg(x + y) = ctgx*ctgy - 1/ ctgx + ctgy

sin(x - y) = sinx*cosy - cosx*siny

cos(x - y) = cosx*cosy + sinx*siny

tg(x - y) = tgx - tgy/ 1 + tgx*tgy

ctg(x - y) = ctgx*ctgy + 1/ ctgx - ctgy

sin 2x = 2 sinx*cosx

cos 2x = cos2x - sin2x = 1 - 2 cos2x = 2 cos2x - 1

tg 2x = 2tgx / (1- 2tgx)

ctg 2x=(ctg2x - 1)/ 2ctgx

sin 3x = sinx(3cos2x - sin2x)= sinx(3 - 4 sin2x)

cos 3x = cosx(cos2x - 3 sin2x) = cosx(4 cos2x - 3)

tg 3x = tgx 3 - tg2x/ 1 - 3 tg2x

ctg 3x = ctgx ctg2x - 3/ 3 ctg2x -1