Reason:

chart

Graphics refer to several spatial shapes that can be divided by contour lines in two-dimensional space, such as straight lines, circles, arcs, arbitrary curves and charts.

corner

(junior high school definition)

A figure composed of two rays with a common endpoint is called an angle.

(high school definition)

The figure formed by the rotation of light from one position to another around its endpoint is called an angle.

Because an angle can be divided into several spatial shapes by contours in two-dimensional space,

So the angle is a number.