This question was previously asked in

MP Sub Engg Official Civil Paper Held on 4 Sep 2018 - Shift 2

Option 3 : 75^{∘ }

CT 1: Building materials

2991

10 Questions
10 Marks
10 Mins

**Given:**

ABCD is a square.

E is a point inside square.

ΔCDE is an equilateral triangle.

**Calculation:**

Let the side of square be a.

ΔCDE is an equilateral triangle. (Given)

∴ ∠CDE = 60°

and, Sides of ΔCDE are also equal to sides of square ABCD.

And, In ΔADE:

Side DE = Side DA = a

∴ ΔADE is an isosceles triangle.

∠ADE = ∠ADC - ∠CDE

⇒ ∠ADE = 90° - 60°

⇒ ∠ADE = 30°

∠AED = (180° - ∠ADE)/2

⇒ (180° - 30°)/2

⇒ 150°/2

⇒ 75°