MathDB

Angle = Angle (twice)

Source: Rioplatense L-2 2022 #4

December 13, 2022

geometryparallelogram

Problem Statement

Let

ABCD

be a parallelogram and

M

is the intersection of

AC

and

BD

. The point

N

is inside of the

\angle MND=\angle NCB

such that

\angle AND=\angle BNC

. Prove that

\angle MNC=\angle NDA

and

\angle MND=\angle NCB

.

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