Circle Tangents
There are four Circles that touch all the sides of a given Triangle. These are all touched bythe Circle through the intersection of the Angle Bisectors of the Triangle, knownas the Nine-Point Circle.
Given the above figure, 
, since
Because
, it follows that .
The line tangent to a Circle of Radius 
centered at 
through
can be found by solving the equation
giving
Two of these four solutions give tangent lines, as illustrated above.See also Kissing Circles Problem, Miquel Point, Monge's Problem, Pedal Circle, Tangent Line,Triangle
References
Dixon, R. Mathographics. New York: Dover, p. 21, 1991. Honsberger, R. More Mathematical Morsels. Washington, DC: Math. Assoc. Amer., pp. 4-5, 1991.
- Casimir Operator
- Cassini Ellipses
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- Catalan Integrals
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- Catalan's Diophantine Problem
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- Catastrophe
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