📐 Part 1: Angle Classification

1. Classify each angle as acute, right, obtuse, or reflex:

a) 45° is:

Acute

Right

Obtuse

Reflex

b) 90° is:

Acute

Right

Obtuse

Reflex

c) 135° is:

Acute

Right

Obtuse

Reflex

d) 200° is:

Acute

Right

Obtuse

Reflex

2. Which of the following statements about angles are correct? (Check all that apply)

An acute angle is less than 90°

A right angle measures exactly 90°

An obtuse angle is greater than 90° but less than 180°

A reflex angle is greater than 180°

The sum of angles in any triangle is 360°

📏 Part 2: Measuring Angles

3. Use your protractor to measure the angles in the triangles below. Record your measurements and classify each angle:

Triangle A:

Angle 1: ______° Classification: ___________

Angle 2: ______° Classification: ___________

Angle 3: ______° Classification: ___________

Sum of angles: ______ + ______ + ______ = ______°

4. Draw a triangle with the following angle measurements and verify they add to 180°:

60°, 70°, and 50°

Verification: ______ + ______ + ______ = ______°

🧮 Part 3: Finding Missing Angles

5. Find the missing angle in each triangle. Show your working:

a) Triangle with angles 45° and 85°. Find the third angle.

Missing angle = ______°

b) Triangle with angles 30° and 120°. Find the third angle.

Missing angle = ______°

c) Triangle with angles 72° and 38°. Find the third angle.

Missing angle = ______°

6. In triangle ABC, angle A = 2x°, angle B = 3x°, and angle C = x°. Find the value of x and each angle:

x = ______

Angle A = ______°

Angle B = ______°

Angle C = ______°

🔄 Part 4: Interior and Exterior Angles

7. Match each term with its correct definition:

1. Interior angle

2. Exterior angle

3. Angle sum property

4. Supplementary angles

A. Two angles that add to 180°

B. An angle inside a triangle

C. Interior angles of a triangle sum to 180°

D. An angle outside a triangle

8. True or False? Circle the correct answer:

The sum of interior angles in any triangle is always 180°:

True

False

An exterior angle equals the sum of the two opposite interior angles:

True

False

A triangle can have two obtuse angles:

True

False

All triangles have at least two acute angles:

True

False

🏗️ Part 5: Real-World Applications

9. A roof truss forms a triangle. If two of the angles measure 35° and 110°, what is the third angle? Explain why this is important for construction:

10. Explain in your own words why the sum of angles in a triangle is always 180°. Give an example to support your explanation:

11. Challenge: In triangle PQR, the exterior angle at vertex P measures 125°. If angle Q = 45°, find angle R. Show your working:

Angle R = ______°

Triangle Angles Worksheet

Triangle Angles Worksheet

📐 Part 1: Angle Classification

📏 Part 2: Measuring Angles

🧮 Part 3: Finding Missing Angles

🔄 Part 4: Interior and Exterior Angles

🏗️ Part 5: Real-World Applications

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