Identify Types of Angle in 2D Shapes (Year 4) | CGP Plus - Free Printable

Let's solve the problem step by step.

Task:

Label all the angles in each of the shapes with:
- A = acute (less than 90°)
- R = right-angle (exactly 90°)
- O = obtuse (greater than 90° but less than 180°)

We’ll go through each shape one by one and identify the type of angles present.

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1. Blue Triangle (Top Left)

This is an equilateral triangle (all sides equal, all angles equal).
- Each angle = 60° → Acute
- All three angles are A

✔ Answer: A, A, A

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2. Purple Square (Top Middle)

All angles in a square are 90°.
- All four angles are Right angles
- All four angles are R

✔ Answer: R, R, R, R

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3. Red Pentagon (Top Right)

This is a regular pentagon (all sides and angles equal).
- Interior angle of a regular pentagon = (5-2) × 180° / 5 = 108°
- 108° > 90° → Obtuse
- All five angles are O

✔ Answer: O, O, O, O, O

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4. Yellow Trapezoid (Middle Left)

This is a trapezoid (one pair of parallel sides).
- Two angles on the same side of the legs are supplementary (add to 180°).
- From visual inspection:
- The two angles adjacent to the longer base appear to be acute (less than 90°)
- The two angles adjacent to the shorter base appear to be obtuse (greater than 90°)
- So: A, O, A, O

✔ Answer: A, O, A, O

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5. Pink Rhombus (Middle Center)

This is a rhombus, not a square (angles not 90°).
- Opposite angles are equal.
- Adjacent angles are supplementary.
- From appearance:
- Two angles are acute (< 90°)
- Two angles are obtuse (> 90°)
- So: A, O, A, O

✔ Answer: A, O, A, O

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6. Blue Right Triangle (Middle Right)

This is a right triangle — one angle is clearly 90°.
- One angle = 90° → R
- The other two angles are acute (since sum of angles = 180°, and one is 90°, the others must add to 90°)
- So: A, R, A

✔ Answer: A, R, A

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7. Blue Irregular Triangle (Bottom Left)

This triangle has one very wide angle (looks like it’s > 90°), so:
- One angle is obtuse (O)
- The other two are acute (A)
- So: A, O, A

✔ Answer: A, O, A

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8. Green Pentagon (Bottom Center)

This is a regular pentagon (like the red one).
- Each interior angle = 108° → Obtuse
- All five angles are O

✔ Answer: O, O, O, O, O

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9. Green Parallelogram (Bottom Right)

This is a parallelogram (opposite sides parallel).
- Opposite angles are equal.
- Adjacent angles are supplementary.
- From appearance:
- Two angles are acute (A)
- Two angles are obtuse (O)
- So: A, O, A, O

✔ Answer: A, O, A, O

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10. Orange Triangle (Bottom Left)

This looks like an isosceles triangle with a very wide top angle.
- Top angle appears obtuse (O)
- Base angles are acute (A)
- So: A, O, A

✔ Answer: A, O, A

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11. Blue Hexagon (Bottom Right)

This is a regular hexagon.
- Interior angle of a regular hexagon = (6-2) × 180° / 6 = 120°
- 120° > 90° → Obtuse
- All six angles are O

✔ Answer: O, O, O, O, O, O

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✔ Final Answers:

| Shape | Angles |
|------|--------|
| 1. Blue Triangle | A, A, A |
| 2. Purple Square | R, R, R, R |
| 3. Red Pentagon | O, O, O, O, O |
| 4. Yellow Trapezoid | A, O, A, O |
| 5. Pink Rhombus | A, O, A, O |
| 6. Blue Right Triangle | A, R, A |
| 7. Blue Irregular Triangle | A, O, A |
| 8. Green Pentagon | O, O, O, O, O |
| 9. Green Parallelogram | A, O, A, O |
| 10. Orange Triangle | A, O, A |
| 11. Blue Hexagon | O, O, O, O, O, O |

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🔍 Summary:

- Acute angles (A): < 90°
- Right angles (R): = 90°
- Obtuse angles (O): > 90°

Use these labels for each angle in the respective shapes.

Let me know if you'd like a labeled version of the image!