Hints :
For question 1 and 2 use this triangle
hint for question 3.
Here is an interactive unit cirlce for trigonometry. Try and work really understand what it is telling you.
WHEN you fully understand it advanced trig will become easier.
Cos of an angle is given by the x value on the circumference of the unit circle. See if you can work out why.
http://www.mathsisfun.com/geometry/unit-circle.html
Here is a mor advanced version.
If you can work out the first one then see if you can make sense of this one.
https://www.mathsisfun.com/algebra/trig-interactive-unit-circle.html