A related theory
1. Tangent circles is perpendicular to the radius shall touch points
2. From some outside the circle. Drag the tangent circle have two lines of equal length. And supports the same Center corner with
3. The two circles touch band. Touch point with the center point of the circle, both as a matter of course on the same straight line
4. The angle formed by the tangent lines to the tangent points at the end of the record, surely equal to the angle on the part of the circle that is the opposite of
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