a^2 + b^2 = c^2....this is the pythagoream theroum (sorry, probably spelled it wrong)....it is used for right triangles.
a and b are ur legs of the triangle and c is the hypotenuse. Therefore, the value of a^2 is the value of one of the legs, squared.
OR. if u mean this..
a^2 + b^2 = c^2
a^2 = c^2 - b^2