The segment CD is tangent to the green circle c, ending on the orange circle d, which also contains the foot of the perpendicular line from C to the diameter of c which extends to D. What is the angle between the two circles?

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## Solution

The angle α is 90°.

AB:AC=AC:AD,

AB×AD=AC^2=AE^2

AE is tangent to the orange circle d (because of Power of point A wrt d)

α=90°