- Aobtuse-angled
- Bequilateral
- Cacute-angled
- Dright-angled
Step-by-Step Solution
The interior angle at that vertex is 180° − 90° = 90°, so the triangle has a right angle.
Answer: D) right-angled
If one exterior angle of a triangle is exactly 90°, the triangle must be:
Class 9Exterior Angle of a TriangleGeometry — Lines and Angles
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