TITLE: How to calculate the middle of a line?
QUESTION [5 upvotes]: My question is following. I have a line with a given $(X_1, Y_1)$ and $(X_2, Y_2)$ coordinates (see figure below). I need to calculate coordinates of the middle of this line $(X, Y)$. I tried to use classical method of finding distance between two coordinates, but it works only when the line is situated horizontally. 
Could anybody help me with a formula to find coordinates of the middle of a given line please?
Thanks beforehand.

REPLY [5 votes]: The midpoint formula