In △ABC above, BC is produced to D, |AB| = |AC|, and ∠BAC = 50°. Find ∠ACD.
Attached Figure / Diagram
A
115°
B
65°
C
60°
D
50°
Verified Correct Answer: A.
Step-by-Step Mathematical Solution
∴ Triangle ABC is isosceles.
:∠ACB = ∠ABC
∠ACD = 180° - ∠ACB (angle on a straight line)
Let ∠ACB = ∠ABC = x
.: 2x + 50 = 180° (sum of angles in a triangle)
2x = 130°
x = 65°
.: ∠ACB = 65° ==> ∠ACD = 180° - 65° = 115°
Source: WAEC / JAMB / NECO Classroom Archive (Record #75910)