Look at the triangle on the right. As you can see the
largest angle is a right angle. A triangle with a right
angle is called a right triangle. The longest side of
a right triangle is called the hypotenuse.
The other two sides are called legs. The legs meet to
form the right angle.

Check out the right triangle below which has a square on each side.
Can you fit the small squares into the big one? Just drag the pieces
with your mouse. Try it out.

(By dragging the black square at the top you can change
the shape of the right triangle.)