You may have chosen this option because it contains $\displaystyle\frac{{1}}{{2}}\usepackage{cmbright}\Huge\$ and $\displaystyle{i}\usepackage{cmbright}\Huge\$ , but it is not equal to $\displaystyle\frac{{1}}{{2}}\usepackage{cmbright}\Huge\$ . A complex number is any number in the form $\displaystyle{a}+{b}{i}\usepackage{cmbright}\Huge\$ where a and b are real numbers. The fraction $\displaystyle\frac{{1}}{{2}}\usepackage{cmbright}\Huge\$ is the real part of this complex number.