Geometry - Angle in Square and Equilateral Triangle

Question

If $ABCD$ is a square and $BCE$ is an equilateral triangle constructed externally on side $BC$, what is the measure of $\angle DEC$?

Accepted Answer

A. In $	riangle CDE$, $CD = CE = BC$. $\angle DCE = 90^\circ + 60^\circ = 150^\circ$. Since $CD = CE$, $\angle DEC = \angle EDC = \frac{180^\circ - 150^\circ}{2} = 15^\circ$.

Answer

$15^\circ$

Answer

$30^\circ$

Answer

$20^\circ$

Answer

$45^\circ$

Geometry - Angle in Square and Equilateral Triangle

Explanation

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