- A70°
- B140°
- C110°
- D40°
Step-by-Step Solution
Base angles = (180° − 40°) ÷ 2 = 70°. Exterior angle at a base vertex = 180° − 70° = 110°. (140° is the exterior angle at the apex.)
Answer: C) 110°
An isosceles triangle has a vertex angle of 40°. What is the exterior angle at either base vertex?
Class 9Exterior Angle of a TriangleGeometry — Lines and Angles
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