f(x)=ln[x+(1+x²)½]
f(-x)=ln[-x+(1+x²)½]
所以
f(x)+f(-x)= ln[x+(1+x²)½]+ln[-x+(1+x²)½]
=ln{[x+(1+x²)½]*[-x+(1+x²)½]}
=ln[ (1+x²)-x²]
=ln1
=0
即f(x)+f(-x)=0
即f(-x)= -f(x)
所以f(x)是奇函数.
f(x)=ln[x+(1+x²)½]
f(-x)=ln[-x+(1+x²)½]
所以
f(x)+f(-x)= ln[x+(1+x²)½]+ln[-x+(1+x²)½]
=ln{[x+(1+x²)½]*[-x+(1+x²)½]}
=ln[ (1+x²)-x²]
=ln1
=0
即f(x)+f(-x)=0
即f(-x)= -f(x)
所以f(x)是奇函数.