You probably mistakenly found $\displaystyle{\log}_{{{4}}}{100}=\frac{{{\ln{{4}}}}}{{{\ln{{100}}}}}\usepackage{cmbright}\Huge\$ , instead of $\displaystyle{\log}_{{{4}}}{100}=\frac{{{\ln{{100}}}}}{{{\ln{{4}}}}}\usepackage{cmbright}\Huge\$ .