- A260°
- B100°
- C130°
- D80°
Step-by-Step Solution
Join AD and produce it past D. Using the exterior angle theorem in both triangles ABD and ACD: ∠BDC = ∠ABD + ∠A + ∠ACD = 20° + 50° + 30° = 100°.
Answer: B) 100°
In the arrowhead figure, ∠A = 50°, ∠ABD = 20° and ∠ACD = 30°. Find ∠BDC (the non-reflex angle, marked ?).
Class 9Exterior Angle of a TriangleGeometry — Lines and Angles
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