Angles on lines, in triangles and quadrilaterals
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The teaching part (1 min) is free to watch. A free account opens the whole lecture: 7 practice questions, 1 real past-paper question with the answer explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
What this lecture covers
- Angle facts are free marks
- Angles at a point
- A straight-line equation
Read the transcript of the teaching part
Last time
Before we start: last time, in Similar triangles and congruent triangles, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.
Angle facts are free marks
Open any paper and you will find an angle question. They are the friendliest marks on the paper, because every answer comes from a short list of facts. Learn the facts, learn the reason words, and you get the answer and the explanation mark every time.
Angles at a point
Angles on a straight line add up to one hundred and eighty degrees. Angles around a point add up to three hundred and sixty degrees. When two straight lines cross, the opposite angles are equal. These are vertically opposite angles.
A straight-line equation
On a straight line, the angles are x, two x and thirty degrees. Add them and set the sum to one eighty. Three x plus thirty is one eighty, so three x is one hundred and fifty. Then x is fifty. Check by adding: fifty plus a hundred plus thirty is one hundred and eighty.
How often it comes up
How often Cambridge has asked each part, counted by ExamYard from every past paper in its question bank: Angles and parallel lines · Angles in triangles and polygons.
The whole chapter: Angles, Polygons and Symmetry.
Chapter 21: Angles and symmetry
- Angles on lines, in triangles and quadrilaterals 6 min
- Angles in polygons and symmetry 6 min
Also for O Level Maths 4024
Which topics come up most in O Level Maths 4024 past papers, counted from every paper since 2004.