Classify Triangles Worksheet: Identify acute, right, and obtuse triangles by their angles.

Explanation:
We need to classify each triangle by its angles:
- Acute triangle: all three angles are less than 90°.
- Right triangle: one angle is exactly 90° (looks like a square corner).
- Obtuse triangle: one angle is greater than 90° (looks “stretched” or “wide” at one corner).

Since we can’t measure angles directly from the drawing, we use visual clues:
- If a triangle looks “pointy” with no wide angles → likely acute.
- If one corner looks like a perfect L-shape (90°) → right.
- If one corner is clearly “open wide” (>90°) → obtuse.

Let’s go one by one:

1.a. Triangle is narrow and all corners look sharp (<90°) → acute
1.b. One angle looks wider than the others — the top angle is clearly >90° → obtuse
1.c. One angle is very wide (the left angle), definitely >90° → obtuse

2.a. All angles look sharp; no wide or right angle → acute
2.b. The left angle looks like a right angle (L-shaped) — the sides seem perpendicular → right
2.c. One angle (bottom-left) is wide — looks >90° → obtuse

3.a. One angle (bottom-right) is very wide → obtuse
3.b. All angles appear less than 90° — triangle is fairly balanced and pointy → acute
3.c. All angles look sharp; symmetric shape → acute

4.a. One angle (top) is wide — clearly >90° → obtuse
4.b. One angle (left) looks like a right angle (sides meet at 90°) → right
4.c. One angle (right side) is wide — looks >90° → obtuse

5.a. One angle (right side) is wide — definitely >90° → obtuse
5.b. All angles look less than 90° — triangle is compact and pointy → acute
5.c. One angle (top) is very wide — >90° → obtuse

Now double-check for any possible right triangles we might have missed:
- 2.b: Yes — the vertical and horizontal sides form a clear right angle.
- 4.b: Also looks like a right triangle (one corner is square-like).
No others show that clean 90° corner.

So final classification per item:

1.a: acute
1.b: obtuse
1.c: obtuse
2.a: acute
2.b: right
2.c: obtuse
3.a: obtuse
3.b: acute
3.c: acute
4.a: obtuse
4.b: right
4.c: obtuse
5.a: obtuse
5.b: acute
5.c: obtuse

Final Answer:
1.a: acute
1.b: obtuse
1.c: obtuse
2.a: acute
2.b: right
2.c: obtuse
3.a: obtuse
3.b: acute
3.c: acute
4.a: obtuse
4.b: right
4.c: obtuse
5.a: obtuse
5.b: acute
5.c: obtuse