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Triangle Properties and Angles
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Triangle Properties and Angles
📐 Part 1: Triangle Classification
1. A triangle with all three sides equal is called:
Scalene
Isosceles
Equilateral
Right-angled
2. Which of these describes an obtuse triangle?
Has one angle equal to 90°
Has one angle greater than 90°
All angles are less than 90°
Has two equal angles
3. Check all properties that apply to an isosceles triangle:
Two sides are equal
Two angles are equal
All sides are different lengths
Has a line of symmetry
4. A triangle has angles of 30°, 60° and 90°. This triangle is:
Acute and scalene
Right-angled and scalene
Obtuse and isosceles
Right-angled and isosceles
🔢 Part 2: Angle Calculations
5. The sum of interior angles in any triangle is always ________°.
6. In a triangle, two angles are 45° and 75°. Calculate the third angle:
Third angle = ________°
7. An isosceles triangle has one angle of 40°. What are the other two angles?
The other two angles are: ________° and ________°
8. In a right-angled triangle, one of the acute angles is 35°. Find the other acute angle:
The other acute angle = ________°
💭 Part 3: Reasoning and Explanation
9. Explain why the sum of angles in any triangle is always 180°. Use a diagram to support your explanation:
10. A triangle has angles in the ratio 1:2:3. Calculate each angle and classify the triangle by its angles:
The angles are: ________°, ________°, and ________°
This triangle is classified as: ________________
11. Explain why it's impossible to have a triangle with angles of 60°, 70° and 80°:
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