You may have correctly determined that the point $\displaystyle{\left(-\frac{\sqrt{{3}}}{{2}},-\frac{{1}}{{2}}\right)}\usepackage{cmbright}\Huge\$ is where the angle $\displaystyle\frac{{{7}\pi}}{{6}}\usepackage{cmbright}\Huge\$ radians or $\displaystyle{{210}}^{\circ}\usepackage{cmbright}\Huge\$ intersects the unit circle. However, you forgot which coordinate corresponds to which function. The x-coordinate gives you the value of the cosine function at that angle, and the y-coordinate gives you the value of the sine function at that angle. The correct answer is: $\displaystyle{\cos{{\left(\frac{{{7}\pi}}{{6}}\right)}}}=-\frac{\sqrt{{3}}}{{2}}{\quad\text{and}\quad}{\sin{{\left(\frac{{{7}\pi}}{{6}}\right)}}}=-\frac{{1}}{{2}}\usepackage{cmbright}\Huge\$