Question 37

$$ABCD$$ is square and $$CDE$$ is an equilateral triangle outside the square. What is the value (in degrees) of $$\angle BEC$$?

Solution

Triangle CDE is equilateral triangle.

So,CE=CD=BC .

So, For triangle BCE, CE=BC .

So, triangle BCE is a isosceles triangle .

So, angle CBE=angle CEB.

Now,angle BCD=90° and angle ECD=60°.

So, angle BCE=90°+60°=150°.

So, 2× angle BEC=180°-150°=30°.

So, angle BEC= 15°.

A is correct choice.

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