exponential implementation uses the series e^x = 1 + x + x^2/2 + x^3/6 + ... natural logarithm uses ln(a) = 2 * ( (a-1)/(a+1) + 1/3 * ((a-1)/(a+1))^3 +... ) log10 uses log10(a) = ln(a)/ln(10) Change-Id: I7303404b2b5a2bf60aad0706ca964a7cea19a27c Reviewed-on: http://gerrit.rockbox.org/333 Reviewed-by: Frank Gevaerts <frank@gevaerts.be>