Two ways to find distance :
1. Plot the two points on the graph and count the grids between them.
2. Use the formula:

where (X1, Y1) and (X2, Y2) are the two coordinates.
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How to use the Pythagorean Theorem to tell if it is right angle triangle:
1. Add the square of the 2 sides together.
2. Root the answer. If it is equal to the third side, it is a right angle triangle.