used to find the hypothesis of a triangle. it is also called the Pythagorean Theorem
If c denotes the length of the hypotenuse and a and b denote the lengths of the other two sides, the Pythagorean theorem can be expressed as the Pythagorean equation:
a 2 + b 2 = c 2 . {\displaystyle a^{2}+b^{2}=c^{2}.}
If the length of both a and b are known, then c can be calculated as
c = a 2 + b 2 . {\displaystyle c={\sqrt {a^{2}+b^{2}}}.}
If the length of the hypotenuse c and of one side (a or b) are known, then the length of the other side can be calculated as
a = c 2 − b 2 {\displaystyle a={\sqrt {c^{2}-b^{2}}}}
or
b = c 2 − a 2 . {\displaystyle b={\sqrt {c^{2}-a^{2}}}.}