MATLAB: How to find a tangent circle is inside a quadrant ellipse

circleellipseMATLABtangent

How to find a tangent circle is inside a quadrant ellipse, the circle is tangent to +x axis, +y axis and the ellipse. half -axis of ellips are a=2 and b=1. what is the diameter of tangent circle (r=?). I solved this problem by iteratively. But I want to solve this problem with closed formula . can you help me? thanks.

Best Answer

Three equation
(x-r)^2+(y-r)^2-r^2; circle equation (x/a)^2+(y/b)^2-1;ellipse equation (b^2*x)/(a^2*y)-(x-r)/(y-r);common tangent equation
and solution of three equations
x= 0.55165767 y= 0.96120677 tangent points r= 0.48305175 (diameter of tangent circle)
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