The number corresponding to a particular point on the number line is called the coordinate of the point.
This correspondence is called a coordinate system. Pythagorean Theorem
In a right triangle, the sum of the squares of the lengths of the
legs is equal to the square of the length of the hypotenuse. Distance Formula
Suppose that P(x1, y1) and R(x2, y2) are two points
in a coordinate plane. Then the distance between
P and R, written d(P,R), is given by the distance
formula.

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