Can someone explain geometric relationships? such as pythagorean theorem ?

so the triangle has 3 sides, keeping in mind that the longest side is always the hypotenuse "c".

so the sides' lengths are 8, 10 and 15, so the legs are 8 and 10, the hypotenuse is 15 hmmmm, well, from the pythagorean theorem, c² = a² + b², meaning the square of the hypotenuse has to equal the sum of the square of the other two, let's see if that's true.