Докажите тождество:

 

sin 2a - tg a = cos 2a tg a

sin^2 a * tg a - cos^2 a== sin^3 a / cos a - 1+ sin^2 a == sin^3 a / sqrt(1-sin^2 a) - 1+ sin^2 a == 1/27 / sqrt(1-1/9) -1 + 1/9 = = 1/(9sqrt(8) -8/9 = = (sqrt(2)-32)/36