Ответы и объяснения

2013-01-21T20:09:56+00:00

f(x) = 1*ctgx + x*tgx = x(ctgx + tgx) = x(sinx/cosx + cox/sinx) = x((sin^2(x) + cos^2(x))/(sinx*cosx + cosx*sinx) = x(1/sinx*cosx + cosx*sinx) = x/cos^2(x) + sin^2(x) = x