I need a bit of help. Take a look at the graph below



What I have there is a semi-circle with a 145 radius. Its lowest point on the Y axis is 10, and the highest is 155. On the X axis it spans from 10 to 300.

How would the function to calculate X based on a given Y look like? The result of the calculation would be a pair of values for X, for example for Y = 155 it would be X1 = 10, X2 = 300. The only single point is for Y = 10 where the result is X = 155.