Answer:
∠ECD is 110°
Step-by-step explanation:
For a cyclic quadrilateral,
∠ABC + ∠AEC = 180°
Therefore ∠AEC = 180° - 45° = 135°
∠CAE + ∠ACE + ∠AEC = 180° (Angles in a triangle)
Therefore ∠CAE = 180 - 20 - 135 = 25°
∠CAE = ∠CDA = 25° (Base angles of isosceles triangle ΔCAD)
∠CED + ∠AEC = 180°(Sum of angles on a straight line)
Therefore ∠CED + 135° = 180°
∠CED = 180° - 135° = 45°
∠ECD + ∠CED + ∠CDA = 180°
Therefore ∠ECD = 180° - (∠CED + ∠CDA)
∠ECD = 180° - (45° + 25°) = 110°
Therefore, ∠ECD = 110°.
