Answer:
Pythagorean theorem
Step-by-step explanation:
Since perpendicular segment is bisector of AB, the distance from A and B to the intersection is equal
Also the angle between those lines is right angle
The distance from C to AB is the line segment that is common side of the triangles formed by connecting end points
So the distance AC = BC as hypotenuse of congruent right triangles
This measurement justifies Pythagorean theorem