Hi guys, I thought I knew how to do these but I've done this question over and over on an online test that you can self check answers and I can't get the right answer.

Here's the situation:

sin(x)=3/4 1st quadrant

sin(y)=1/2 2nd quadrant

As, cos(x)=sqrt(1-sin^2(x))

cos(x) =sqrt(7)/(4)

cos(y)=sqrt(-3)/(2)

cos(x+y)=cos(x)cos(y)+sin(x)sin(y)

and I get OVER AND OVER this answer: 3/8-sqrt(21)/8

I spent about half an hour trying to use LaTex to no avail. Sorry.

If someone can grind out something different and post that'd be wonderful.