PRECALCULUS (Trig Functions) -SO LOST

I am having a serous issue with these two problems. No matter what formula's I use i keep getting the wrong answer. I NEED HELP BADLY.

1.) 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((11pi)/8) =

sin(-(pi/12)) =

cos((3pi)/8) =

cos((11pi)/8) =

&

2.) If cos(t) = - (3/5) where pi < t < ((3pi)/2), find the values of the following trigonometric

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).

cos(2t) =

sin(2t) =

cos(t/2) =

sin(t/2) =

Any and all Help greatly appreciated

~Kiba~