You cannot assume you will have two isoceles triangles after the imaginary line draw between the points, if this were the case then for the triangle on the left, you would not have two known sides of radical 3 and 1, using the theory of Pythagorus, we know that the length of the hypotenuse for the left triangle formed after drawing a line connecting the two points is 2.
Because all radii are equal, the other radii must be 2 as well, using the theorem again, we find that the connecting line must be equal to radical 8, simplified to 2 radical 2.
Now given that from point P to the y axis is radical 3, we solve for what is needed to be added to radical 3 to equate to 2 radical 2, in decimal form, for accuracy, we find that radical 3 (1.73205) plus X = 2 radical 2 (2.82842), solve for X, X=1.0963, or ~1.
DO NOT assume two isoceles triangles are formed, just because it works out once, does not hold true always.