Use a sum or difference formula or a half angle formula to determine the value of the trigonometric functions. Give exact answers. Do not use decimal numbers. The answer should be a fraction or an arithmetic expression. If the answer involves a square root it should be enter as sqrt; e.g. the square root of 2 should be written as sqrt(2).

$\sin(-\frac{\pi}{12})$ =
$\sin(\frac{5\pi}{12})$=
$\cos(-\frac{\pi}{12})$=
$\cos(\frac{11\pi}{8})$=