производная от (5+tg^3x)^3
((5+tg^3x)^3)'=3* (5+tg^3x)^(3-1) * (5+tg^3x)'=3* (5+tg^3x)^2 * ((5)'+(tg^3 x)')=
=3* (5+tg^3x)^2 *(0+3*tg^(3-1) x *(tg x)')=3* (5+tg^3x)^3 * tg^2 x/cos^2 x
y'=3(5+tg^3x)^2 * (0+1/cos^6x)