y=(1+x²) *ln[x+√(1+x²)]
那么求导得到
y'=(1+x²)' *ln[x+√(1+x²)] + (1+x²) *ln[x+√(1+x²)] '
显然
(1+x²)'=2x
而ln[x+√(1+x²)] '
=1/[x+√(1+x²)] * [x+√(1+x²)]'
=1/[x+√(1+x²)] * [1+ x/√(1+x²)]
=1/√(1+x²)
所以得到
y'=2x *ln[x+√(1+x²)] + (1+x²)/√(1+x²)
=2x *ln[x+√(1+x²)] +√(1+x²)