Midpoint calculator

The midpoint is (A + B) / 2 on each axis, and the other formulas fall out of it: the missing endpoint is 2·M − A, the section point at m:n is (n·A + m·B) / (m + n), and the distance takes a square root, which is why it is the one number here that usually cannot be written as a clean fraction. A vertical pair has an undefined slope and prints its line as x = c instead.