1) Look first at
This comes from an isosceles right-angled triangle with sides, using Pythagoras, . You should see then that , and so .
To solve , simply take this value of from , because .
A more advanced answer, involving radians is the general solution , but if you haven't covered that sort of thing in your course, you can ignore this!
2) . Draw a 30 - 60 - 90 triangle, with a hypotenuse 2 units long, and figure out the lengths of the shortest side using the fact that this triangle is half of an equilateral triangle. Then you should see that the sine of one of the angle is
3) . Use the same formula as in (1), and the fact that .
Can you complete them now?