Question

Найдите ctg(x-y), если cos(x+3y)+cos(3x+y)=1 и sin(x+3y)-sin(3x+y)=1/3

Answer 1

1) y'=1/(sin^2(1-x)) 2) y'=-sinx^3*3x^2+6x 3) y'=2x*tgx+x^2*1/(cos^2x) 4) y'=cos(tgx)*1/(cos^2x)