Diagonal Calculator

This calculator works out the diagonal of a rectangle from its two sides, and the space diagonal of a rectangular box from its three edges, drawing the shape to scale with the diagonal marked. It also runs the other way: give it a diagonal and an aspect ratio, such as 65 inches at 16:9, and it returns the width and height that implies, which is the measurement a wall or a cabinet is checked against. A fourth action counts how many diagonals a polygon with a given number of sides has. Results include the area, the perimeter and the angle the diagonal makes with each side. All of it is Pythagoras, so the units are whatever you enter and the answer comes back in the same ones.