Теория:

Pythagorean Theorem: In a right triangle, the square of the hypotenuse is equal to the sum of the squares of the other two sides.
pythagores.png
 
In the above right triangle \(ABC\), the legs are \(AB\) and \(BC\), and the hypotenuse is \(AC\).
 
So it can be written as, \(AC² = AB² + BC²\).
 
Here \(BC = a, AB = b\) and \(AC = c\).
 
Substituting the known values,
 
\(c² = a² + b²\).