Geometry and TrigonometryHardAngle formed by a bisector in an isosceles triangle
Geometry and Trigonometry practice question
In triangle ABC, AB = AC and angle A measures 36°. The bisector of angle B meets side AC at point D. What is the measure, in degrees, of angle BDC?
Answer: 72
Angles B and C are each 72°, so angle ABD is 36°; angle BDC is the exterior angle of triangle ABD, equal to 36 + 36 = 72.
Common wrong answers
- If you answered 36
- 36 is angle ABD, not angle BDC.
- If you answered 54
- 54 halves 108.
- If you answered 108
- 108 is angle ADB, the supplement.
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