It appears that you found the value of $\displaystyle{\cos{{\left(\frac{{{3}\pi}}{{2}}\right)}}}\usepackage{cmbright}\Huge\$ . Perhaps you made a mistake when converting from radians to degrees. You need to multiply a radian measure by $\displaystyle\frac{{{180}}^{\circ}}{\pi}\usepackage{cmbright}\Huge\$ to convert to degrees. So $\displaystyle\frac{{{3}\pi}}{{4}}\usepackage{cmbright}\Huge\$ radians equals $\displaystyle{{135}}^{\circ}\usepackage{cmbright}\Huge\$ . Find the x-coordinate of the point where $\displaystyle{{135}}^{\circ}\usepackage{cmbright}\Huge\$ intersects the unit circle.