An angle is the amount of turn between two directions. Whenever we rotate or turn, we create an angle. Angles help us describe direction changes in everyday life.
Key Concepts
Right Angle: A quarter turn (90 degrees). The corner of a square is a right angle.
Straight Angle: A half turn (180 degrees). It looks like a straight line.
Full Turn: A complete rotation (360 degrees) brings you back to where you started.
- Types of Angles:
- Acute angle: Less than 90 degrees (e.g., 45 degrees)
- Right angle: Exactly 90 degrees
- Obtuse angle: More than 90 degrees but less than 180 degrees (e.g., 120 degrees)
- Straight angle: Exactly 180 degrees
- Reflex angle: More than 180 degrees but less than 360 degrees
Clockwise and Anticlockwise Turns: Clockwise turns go in the direction clock hands move. Anticlockwise (or counter-clockwise) goes the opposite way.
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Meena faces North and makes a quarter turn clockwise. Which direction does she face?
- Quarter turn clockwise from North = East
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A clock hand moves from 12 to 3. What angle does it turn through?
- From 12 to 3 is a quarter of a full circle.
- Angle = 1/4 x 360 = 90 degrees (a right angle)
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How many right angle turns make a full turn (360 degrees)?
- Full turn / right angle = 360 / 90 = 4 right angles
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Name the type of angle: 150 degrees.
- 150 degrees is more than 90 but less than 180.
- It is an obtuse angle.
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Ravi faces West and turns anticlockwise by a half turn. Where does he face?
- Half turn (180 degrees) anticlockwise from West = East
- (Any half turn reverses direction.)
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Key Facts
Key formulas
Common mistakes
- Mixing up clockwise and anticlockwise results. Always use a compass or imagine a clock face to decide.
- Thinking a straight angle is not an angle. A straight angle (180 degrees) is a valid angle.
Summary
Angles measure the amount of turn. A right angle = 90 degrees, a straight angle = 180 degrees, and a full turn = 360 degrees. Angles can be acute, right, obtuse, straight, or reflex.