📖Definition
An angle is formed when two rays (or line segments) meet at a common point called the vertex. Angles are measured in degrees (°) and describe the amount of rotation between the two rays. A full rotation is 360°.
📐Formula
Angles are classified by their measure: acute (< 90°), right (= 90°), obtuse (90° < angle < 180°), straight (= 180°), reflex (> 180°).
📝Step-by-Step Guide
Identify the Type of Angle
Determine if the angle is acute, right, obtuse, straight, or reflex based on its appearance or measure.
Measure with a Protractor
Place the protractor's center on the vertex, align one ray with the baseline, and read the degree measure.
Use Angle Relationships
Complementary angles sum to 90°. Supplementary angles sum to 180°.
Find Unknown Angles
Use relationships and properties to calculate missing angle measures.
⚠️Common Mistakes to Avoid
- Reading the wrong scale on a protractor
- Confusing complementary and supplementary
- Forgetting that angles in a triangle sum to 180°
- Not identifying the vertex correctly
- Mixing up acute and obtuse angles
✏️Practice Problems
What type of angle is 45°?
Answer: Acute angle
Two angles are complementary. One angle is 35°. What is the other?
Answer: 55°
In a triangle, two angles are 65° and 48°. Find the third angle.
Answer: 67°
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