we find out the hypotenuse .this is all Pythagoras theorem.
1sq.+1sq. = (ur 2) sq. is the unit triangle of Pythagoras theorem
( sq. =square, ur =under root)
all other are multiplication of this unit.
Now what about the right angled triangle which is not having their two sides same length (other than hypotenuse).this type of triange share their hypotenuse with the triangle having both the sides equal length.