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Find <BAD + CDA if B'C' = AB+CD

Source: International Zhautykov Olympiad 2012 - D2 - P2

January 31, 2012

complex numbersgeometry unsolvedgeometry

Problem Statement

Equilateral triangles

ACB'

and

BDC'

are drawn on the diagonals of a convex quadrilateral

ABCD

so that

B

and

B'

are on the same side of

AC

, and

C

and

C'

are on the same sides of

BD

. Find

\angle BAD + \angle CDA

B'C' = AB+CD