Introduction to Lines & Angles (OCR GCSE Maths) : Revision Note

Jamie Wood

Written by: Jamie Wood

Reviewed by: Dan Finlay

Updated on

Properties of Lines & Angles

What properties do I need to know about lines?

  • A line is a straight, one dimensional path that extends forever

    • A line segment is a part of a line, it has a start and an end point

    • A line segment that starts at the point A and ends at the point B is usually labelled AB 

    • Two lines with single marks are of equal length

      • Two other lines with double marks are of (a different) equal length

  • Two lines are parallel if they continue in the same direction as each other forever

    • Parallel lines never intersect (meet)

    • Parallel lines should be marked with arrows

      • If there is more than one pair (or set) of parallel lines in a diagram then multiple arrows will be used

        Diagonals of a parallelogram
  • Two lines are perpendicular if they intersect at right-angles (90°)

What properties do I need to know about angles?

  • When two lines intersect (meet) they will form an angle

  • There are different types of angles  

    • An angle that is less than 90° is called an acute angle

    • An angle that is exactly 90° is called a right angle

    • An angle that is greater than 90° and less than 180° is called an obtuse angle

    • An angle that is exactly 180° is called a straight angle

    • An angle that is greater than 180° but less than 360° is called a reflex angle

types of angle - acute, right, obtuse, reflex
  • Angles at a point add up to 360°

  • Angles on a straight line add up to 180°

    • Angles that add up to 180° are called supplementary angles 

      • e.g. 30 and 150 degrees are supplementary angles

Examiner Tips and Tricks

  • Do not assume two lines are parallel or perpendicular just because they look it, always look out for the arrows or right angle in a diagram, or read the question to look for clues 

Worked Example

Write down the mathematical name for an angle which is greater than 90° but less than 180°.

An obtuse angle

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Jamie Wood

Author: Jamie Wood

Expertise: Maths Content Creator

Jamie graduated in 2014 from the University of Bristol with a degree in Electronic and Communications Engineering. He has worked as a teacher for 8 years, in secondary schools and in further education; teaching GCSE and A Level. He is passionate about helping students fulfil their potential through easy-to-use resources and high-quality questions and solutions.

Dan Finlay

Reviewer: Dan Finlay

Expertise: Maths Lead

Dan graduated from the University of Oxford with a First class degree in mathematics. As well as teaching maths for over 8 years, Dan has marked a range of exams for Edexcel, tutored students and taught A Level Accounting. Dan has a keen interest in statistics and probability and their real-life applications.

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