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Consider a concave kite $ABCD$ with $AB = AD$ and $BC = CD$
Want to show that angle $ABC$ = angle $ADC$
Is it sufficient to say that since the triangles have $AC$ in common, they are congruent by $SSS$. Therefore angle $ABC$ = angle $ADC$?
The reason I ask is that I read this article where the author shows the triangles are congruent (same assumptions, second section of the page), but does not use the $SSS$ criterion which is strikingly easier?
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$\begingroup$Yes, you can indeed use the $SSS$ congruity criterion, and it is very probable that it is the easiest way.
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