y=x^x
logy=log(x^x)=xlogx
(1/y)y'=1+logx
y'=y(1+logx)=(x^x)(1+logx)

y=a^x
logy=log(a^x)=x(loga)
(1/y)y'=loga
y'=y(loga)=(a^x)loga