Parallelogram Isogonality Lemma

by henderson, Jul 17, 2016, 12:58 PM

$\color{red}\textbf{Lemma.}$ The point $P$ lies inside triangle $ABC$ so that $\angle ABP = \angle PCA.$ The point $Q$ chosen such that $PBQC$ is a parallelogram. Prove that $\angle QAB = \angle CAP.$
(taken from liberator's blog)
This post has been edited 2 times. Last edited by henderson, Sep 15, 2016, 11:25 AM
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isogonality

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