This only works for right angled triangles!
Examiners love to give you “distance between two points” questions that involve this theorem.
Example: Find the distance between points (1,-4) and (6,3) on the graph.
If given a question like this simply draw a right angled triangle matching up the two points and find the length of the two shorter sides.
So here the shorter sides are 7 and 5.
72 + 52 = 49 + 25 = 74
So the distance between the points = √ 74 = 8.602 (3 d.p.).