IGCSEMathsEdexcelMaths AFoundationRevision Notes4. Geometry & TrigonometryAngles in Polygons & Parallel LinesAngles around Points & Lines

Angles around Points & Lines (Edexcel IGCSE Maths A: Foundation): Revision Note

Exam code: 4MA1

Written by: Jamie Wood

Reviewed by: Dan Finlay

Updated on 19 January 2026

Basic angle properties

What are the basic angle properties?

Angles around a point add up to 360°
Angles that form a straight line add up to 180°
Vertically opposite angles are equal
- Vertically opposite angles occur when two lines intersect, as in the diagram below

Examiner Tips and Tricks

Use the angle properties to find any missing angles that you can, and mark them on the diagram

Even if they are not the angle you are trying to find, they may help provide a clue!

Worked Example

The diagram below shows three straight lines intersecting at a point.

Find the values of $x$ and $y$ .

Answer:

Vertically opposite angles between two intersecting lines are equal

$x = 25$

Angles that meet on a straight line add up to 180°

$\begin{array}{rcl} x + y + 98 & = & 180 \\ 25 + y + 98 & = & 180 \\ 123 + y & = & 180 \end{array}$

Solve to find $y$

$y = 180 - 123 y = 57$

$x = 25, y = 57$

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