Answer:
1 / f = 1 / p + 1 / q
Explanation:
Mirror problems can be solved analytically with the constructor equation
1 / f = 1 / p + 1 / q
An approximate solution can also be given using graphical methods, where two of three rays must be drawn,
1) A ray that passes through the focal length and bounces horizontally
2) A ray that passes through the center of curvature (c = 2f) of the mirror and does not deviate
3) A beam that comes horizontal and bounces through the focal
The attached shows the ray that passes through the focal length and bounces horizontally.
