奇函数f(-x)=-f(x)
均为奇函数
①f(-x)=ln[-x+√(1+(-x)²)]
=ln{[-x+√(1+(-x)²)][-x-√(1+(-x)²)]/[-x-√(1+(-x)²)]}
=ln[1/[x+√(1+(-x)²)]
=-ln[x+√(1+(-x)²)]
=-f(x)
②f(-x)=1/(2⁻ˣ+1)-½
=2ˣ/(1+2ˣ)-½
=(2ˣ+1-1)/(1+2ˣ)-½
=1-1/(1+2ˣ)-½
=-1/(1+2ˣ)+½