Find cos Θ if sin Theta = a/2. Assume the terminal side of the angle falls in Quadrant 2. Show all work.

Find sin Θ if tan Theta = d/4. Assume the terminal side of the angle falls in Quadrant 1. Show all work.
For the second problem, I have worked out d/4 +1= 1/cos^2 theta But I am unable to figure out what to do from there on.

Question

Find cos Θ if sin Theta = a/2.  Assume the terminal side of the angle falls in Quadrant 2.  Show all work.

Find sin Θ if tan Theta = d/4.  Assume the terminal side of the angle falls in Quadrant 1.  Show all work.
For the second problem, I have worked out d/4 +1= 1/cos^2 theta  But I am unable to figure out what to do from there on.

anonymous · Answer

$$\cos(\theta) = \sin(\theta+\frac\pi2) = \sin(\theta+90^\circ)$$

loser66 · Answer

still need help?

anonymous · Answer

Yes please. I am still stuck on the second problem :)

loser66 · Answer

you got the first one? show me your stuff, please . (the first one)

anonymous · Answer

Not exactly, I tried using what broken symmetry had put but I had gotten confused. 
|dw:1389237119998:dw|
cos= -2/ 2 sqrt3
since cos is x/r

loser66 · Answer

ok, I guide you step by step , for the first one, the triangle in quadrant 2 has the shape like this|dw:1389237096883:dw|