How to solve a right triangle when given only the hypotenuse?

I'm stumped by this question. "Find the perimeter of a regular pentagon inscribed in a unit circle (a circle with radius 1)." I have to find one side of a triangle to solve the problem but I can't figure out how to find the one side when I'm only given a hypotenuse measure of 1. It's a right triangle and there are no other angles and no other measurements.