Identify triangles based on their angles and sides.

Let’s go triangle by triangle. We’ll look at two things for each:

1. Angles — Are all angles less than 90°? (acute)
Is one angle exactly 90°? (right)
Is one angle more than 90°? (obtuse)

2. Sides — Are all sides different? (scalene)
Are two sides the same? (isosceles)
Are all three sides the same? (equilateral)

We’ll use both to name each triangle.

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Triangle 1: All angles are less than 90° → acute. Two sides marked equal → isosceles.
→ Acute isosceles triangle

Triangle 2: One angle is 135° → that’s obtuse. All sides different lengths → scalene.
→ Obtuse scalene triangle

Triangle 3: Has a right angle symbol → right. All sides different → scalene.
→ Right scalene triangle

Triangle 4: Has a right angle → right. Two sides marked equal → isosceles.
→ Right isosceles triangle

Triangle 5: All angles less than 90° → acute. All sides different → scalene.
→ Acute scalene triangle

Triangle 6: One angle is 120° → obtuse. Two sides marked equal → isosceles.
→ Obtuse isosceles triangle

Triangle 7: All angles less than 90° → acute. All sides different → scalene.
→ Acute scalene triangle

Triangle 8: All angles less than 90° → acute. All sides different → scalene.
→ Acute scalene triangle

Triangle 9: All angles less than 90° → acute. All sides different → scalene.
→ Acute scalene triangle

Triangle 10: Has a right angle → right. All sides different → scalene.
→ Right scalene triangle

Triangle 11: One angle is 120° → obtuse. Two sides marked equal → isosceles.
→ Obtuse isosceles triangle

Triangle 12: All angles less than 90° → acute. Two sides marked equal → isosceles.
→ Acute isosceles triangle

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Final Answer:
1. Acute isosceles
2. Obtuse scalene
3. Right scalene
4. Right isosceles
5. Acute scalene
6. Obtuse isosceles
7. Acute scalene
8. Acute scalene
9. Acute scalene
10. Right scalene
11. Obtuse isosceles
12. Acute isosceles