Refer to the $\displaystyle{{45}}^{\circ}-{{45}}^{\circ}-{{90}}^{\circ}\usepackage{cmbright}\Huge\$ triangle. From there you can see that $\displaystyle{{\tan{{45}}}}^{\circ}={1}\usepackage{cmbright}\Huge\$ . It follows that $\displaystyle{x}={{45}}^{\circ}\usepackage{cmbright}\Huge\$ . You may have mistakenly found $\displaystyle{{\sin{{45}}}}^{\circ}\usepackage{cmbright}\Huge\$ .