Measuring angles

It all starts with angles in trigonometry. There are two main ways to measure angles – degrees and radians. Radians are almost exclusively used in quantum computing, but you are probably more familiar with degrees, so we'll start there.

Degrees

There are 360 degrees in a circle. Probably the most familiar use of degrees is in a compass, as shown in the following:

Figure 12.1 – Compass

However, on the X-Y plane, zero degrees starts on the right side of the x axis and goes from there. In fact, the X-Y plane can be broken up into four quadrants with each taking up 90 degrees, as shown in the following:

Figure 12.2 – Four quadrants [2]

Additionally, angle measures can be expressed in negative form. When degrees or radians are positive, you go in the counterclockwise direction, and when they are negative, you go in a clockwise direction on the X-Y plane, as shown in the following diagram:

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