Types of Angles
Learning to classify angles based on their measure.
Core concept
A right angle, exactly 90°, appears frequently in daily life — the corners of a book, a door frame, or a wall meeting the floor are all typically right angles. Angles smaller than a right angle appear 'sharp' (acute), while angles larger appear 'wide' or 'open' (obtuse). Recognising angle types helps in constructing shapes accurately and understanding more advanced geometric concepts like angle sums in polygons.
Exam highlight
Key diagram

- Show examples of acute, right, obtuse, and straight angles with their measures.
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Quick notes
• Acute angle: less than 90°. Right angle: exactly 90°. Obtuse angle: between 90° and 180°.
• Straight angle: exactly 180°. Reflex angle: between 180° and 360°.
• Right angles commonly appear in daily life, like book corners and door frames.
• Recognising angle types is essential for accurate geometric construction.