Mathematics·Geometry · NSSCO 5.1
Angles, lines & parallel lines
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Angles are everywhere — in every corner, every road junction, every roof. In this lesson we learn to name the types of angle, then master the four rules the exam loves: angles on a straight line add to 180°, angles at a point add to 360°, vertically opposite angles are equal, and the parallel-line rules — corresponding, alternate and co-interior angles. Best of all, we practise 'angle chasing': finding an unknown angle step by step, and always writing the reason in words, exactly the way the marker wants it.
What you'll learn in this lesson
By the end you should be able to (NSSCO Mathematics 5.1):
- Name the types of angle: acute, right, obtuse, straight and reflex
- Use and interpret the terms parallel, perpendicular and intersecting lines
- Use the rule that angles on a straight line add up to 180°
- Use the rule that angles at a point add up to 360°
- Use the rule that vertically opposite angles are equal
- Find angles in parallel lines using corresponding, alternate and co-interior (allied) angles
- Solve angle-chase problems, always giving the reason in words
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