Finding an Angle Coterminal with an Angle Measuring Less Than 0°

Since $\mathrm{45°}$ is half of $\mathrm{90°},$ we can start at the positive horizontal axis and measure clockwise half of a $\mathrm{90°}$ angle.

Because we can find coterminal angles by adding or subtracting a full rotation of $\mathrm{360°},$ we can find a positive coterminal angle here by adding $\mathrm{360°}.$

We can then show the angle on a circle, as in Figure 19.