Derousseau's Generalization of the Malfatti circles

Angle Bisectors (3)


[Other solutions]
[Guy]
[Lob & Richmond]

\(\mathbf{2c}\) \((130)\)

\[\begin{aligned}\overrightarrow{AA^{\prime}}&=\dfrac{1-{\cos\dfrac{A}{2}}-{\cos\dfrac{B}{2}}+{\sin\dfrac{C}{2}}-{\sin\dfrac{A}{2}}+{\sin\dfrac{B}{2}}+{\cos\dfrac{C}{2}}}{2\left(1+{\cos\dfrac{A}{2}}+{\sin\dfrac{B}{2}}+{\cos\dfrac{C}{2}}\right)}\overrightarrow{A{I_C}},\\\overrightarrow{BB^{\prime}}&=\dfrac{1+{\cos\dfrac{A}{2}}+{\cos\dfrac{B}{2}}+{\sin\dfrac{C}{2}}-{\sin\dfrac{A}{2}}+{\sin\dfrac{B}{2}}+{\cos\dfrac{C}{2}}}{2\left(1-{\sin\dfrac{A}{2}}-{\cos\dfrac{B}{2}}+{\cos\dfrac{C}{2}}\right)}\overrightarrow{B{I_C}},\\\overrightarrow{CC^{\prime}}&=\dfrac{1+{\cos\dfrac{A}{2}}-{\cos\dfrac{B}{2}}-{\sin\dfrac{C}{2}}-{\sin\dfrac{A}{2}}+{\sin\dfrac{B}{2}}+{\cos\dfrac{C}{2}}}{2\left(1-{\sin\dfrac{A}{2}}+{\sin\dfrac{B}{2}}+{\sin\dfrac{C}{2}}\right)}\overrightarrow{C{I_C}}.\end{aligned}\]

Hiroyasu Kamo