Calc
posted by Chelsea .
Find an expression for the function whose graph is the given curve.
The top half of the circle x^2 + (y2)^2 = 4
Please Help. I don't even know where to start.

Hints:
1. Solve for y in terms of x.
2. You will have an expression involving a squareroot of an expression.
3. You will need to restrict the expression under the radical to be nonnegative, or else you will end up with a complex quantity.
4. For the top half of the curve (circle), restrict the value of the squareroot to be nonnegative, i.e. take the positive value of the squareroot only. 
So what do you mean by y in terms of x? I solved x^2 + (y2)^2 = 4 and I got y^2  4y + 8 = x^2 ?

I would isolate y on the left like:
(y2)²=4x²
and take squareroot on both sides.
transpose the 2 to the right and you'll get your f(x)=y=....