y= tanx的导数怎么求？

Question

如题所述

Answer 1

y=tan(x+y) 两边求导,用公式(tany)=sec²y*y'
y'=sec²(x+y)(x+y)'
y'=sec²(x+y)(1+y')
y'=sec²(x+y)+y'sec²(x+y)
y'[1-sec²(x+y)]=sec²(x+y)
y'=sec²(x+y)/[1-sec²(x+y)]
=-sec²(x+y)/tan²(x+y),用公式(1-sec²x)=-(sec²x-1)=-tanx
=-1/cos²(x+y)*cos²(x+y)/sin²(x+y),约掉cos²(x+y)
=-1/sin²(x+y)
=-csc²(x+y)