You may have correctly found $\displaystyle\frac{{{210}\pi}}{{180}}\usepackage{cmbright}\Huge\$ , but then reduced incorrectly. To convert from degrees to radians, multiply the degree measure by $\displaystyle\frac{\pi}{{{180}}^{\circ}}\usepackage{cmbright}\Huge\$ . Reduce the fraction using common factors of the numerator and denominator. The correct answer is $\displaystyle\frac{{{7}\pi}}{{6}}\usepackage{cmbright}\Huge\$ .