Two quadrilaterals $ABCD$ and $A_1B_1C_1D_1$ are mutually symmetric with respect to the point $P$. It is known that $A_1BCD$, $AB_1CD$ and $ABC_1D$ are cyclic quadrilaterals. Prove that the quadrilateral $ABCD_1$ is also cyclic
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Tags: geometry, cyclic quadrilateral
SHREYAS333
06.03.2019 15:55
Angle chase also works @below Directed angles as there are many configurations
AlastorMoody
06.03.2019 16:15
Simple angle chasing, and usage of congruent triangles