sin2x + cos2x = 1
tgx = sinxcosxctgx = cosxsinx
tgx ctgx = 1
tg2x + 1 = 1cos2xctg2x + 1 = 1sin2xФормулы двойного аргумента
sin2x = 2sinx cosx
sin2x = 2tgx = 2ctgx = 21 + tg2x1 + ctg2xtgx + ctgx
cos2x = cos2x - sin2x = 2cos2x - 1 = 1 - 2sin2x
cos2x = 1 - tg2x = ctg2x - 1 = ctgx - tgx1 + tg2xctg2x + 1ctgx + tgxtg2x = 2tgx = 2ctgx = 21 - tg2xctg2x - 1ctgx - tgxctg2x = ctg2x - 1 = ctgx - tgx2ctgx2