## Contents

## Related FormulaeEdit

## Tangent FormulaeEdit

In the last row of expressions, if then the trigonometric functions are all positive so the positive sign is needed before the square root.

## DerivationsEdit

Using cofunctions we know that . Use the formula for and cofunctions we can write

Having derived we replace with and use the fact that cosine is even and sine is odd.

## Related FormulaeEdit

## DerivationsEdit

Using and the fact that cosine is even and sine is odd, we have