Hypotenuse and Legs

A right triangle has names for its sides. The side opposite the right angle is the hypotenuse; it is always the longest side. The two sides that make the right angle are the legs.

Here the square is at A, so the legs are AB and AC, the two sides that meet at A. The hypotenuse is BC, the side that does not touch A. Always find the square first; the names follow from it, whatever way the triangle is turned.