Sine-cosine square identity
One trigonometric identity states that for any angle
For a unit triangle (one where the hypotenuse has length 1), the lengths of
the two other sides correspond to the sine and cosine of the angle
In other words, the side opposite to angle
From the pythagorean theorem, we know that for any right triangle with sides of
lengths
In this case:
So we can substitute these values into the pythagorean theorem!
which is otherwise written as: