關於三角函數隱函數的一條問題.

y+tan x=x sec^2 x
d/dx(y/tan x)=d(x sec^2 x)
dy/dx+d(tan x)/dx=(sec^2 x)dx/dx+x d/dx(sec^2 x)
dy/dx+sec^2 x=sec^2 x+x d(sec^2 x)/d(sec x) d(sec x)/dx
dy/dx=x(2sec x)(sec x tan x)=2xsin x/cos^3 x
cos^3 x dy/dx=2xsin x


希望你睇得明...