- AThe triangle is equilateral
- BAB = AC
- C∠A = 90°
- DAB = BC
Step-by-Step Solution
Equal exterior angles mean equal interior angles ∠B = ∠C (each is 180° minus the exterior angle). Sides opposite equal angles are equal, so AB = AC.
Answer: B) AB = AC
In △ABC, BC is produced both ways and the two exterior angles at B and C are equal. What can you conclude?
Class 9Exterior Angle of a TriangleGeometry — Lines and Angles
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