01 Key Concepts
Angle Definition
Formed by two rays sharing a common endpoint (the vertex), measured in degrees.
Types of Angles
Acute (less than 90°), right (exactly 90°), obtuse (between 90° and 180°), straight (exactly 180°).
Complementary Angles
Two angles whose measures add up to exactly 90°.
Supplementary Angles
Two angles whose measures add up to exactly 180°.
Vertical Angles
The pair of opposite angles formed when two lines cross; vertical angles are always equal to each other.
02 Key Formulas
- Complementary angles sum to 90°
- Supplementary angles sum to 180°
03 Solved Examples
Example 1 An angle measures 35°. Find its complement.
- Complementary angles sum to 90°.
- 90 - 35.
Answer: 55°
Example 2 An angle measures 110°. Find its supplement.
- Supplementary angles sum to 180°.
- 180 - 110.
Answer: 70°
Example 3 Classify a 95° angle.
- 95° is greater than 90° but less than 180°.
Answer: Obtuse angle
04 Practice Questions
1Find the complement of a 40° angle.
50°
2Find the supplement of a 130° angle.
50°
3Classify a 45° angle.
Acute
4Classify a 180° angle.
Straight
5If two lines cross, what do we call the opposite (equal) angle pairs formed?
Vertical angles
📄 Angles — Downloadable Worksheet
10 questions with a full answer key. Grab the PDF to print, or try the interactive version in your browser.