To convert from degrees to radians, multiply the degree measure by $\displaystyle\frac{\pi}{{{180}}^{\circ}}\usepackage{cmbright}\Huge\$ :

$\displaystyle{{315}}^{\circ}={{315}}^{\circ}\cdot\frac{\pi}{{{180}}^{\circ}}=\frac{{{315}\pi}}{{180}}=\frac{{{7}\pi}}{{4}}\usepackage{cmbright}\Huge\$