Below is a portion of an ellipse. The semi-minor axis has length 5. A 45 degree diagonal line from the centre to the edge of the ellipse has length 7.
What is the length of the semi-major axis?
If it helps, the general equation for an ellipse is:
(x/a)^2 + (y/b)^2 = 1, where a and b are the two semi-axes.