log(A^B) = BlogA

令 x = logA, y = logB, z=log(A^B) 。2^x = A, 2^y = B, 2^z = A^B, 则有 2^z = A^B = (2^x)^{^}(2^y) = 2^{x(2^y)} ，有z = x*2^y，即 log(A^B) = BlogA。