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Right angled trigonometry

Right angled trigonometry for A Level Law Edexcel Higher: what it means, how to set the working out, and the questions it is asked in.
  • A Level
  • Edexcel
  • Law
  • Higher
  • Spec G18 · G11 · G15
  • 5 min read
  • 6 revision boxes

Introduction

2 boxes
2 min read

What is right angled trigonometry?

Listen to this box

Transcript

A short spoken summary of right angled trigonometry and where it is used.

A spoken walk-through of right angled trigonometry before you read the notes.
The specification wording is precise here, and the mark scheme follows that wording exactly.
Worth knowing: ×10\times 10 moves every digit one column left.
4 rows

The right angled trigonometry reference table

Read the units in the question before you start; a converted unit is the most common slip.
The layout below is the one the mark scheme expects.

Diagram showing right angled trigonometry laid out step by step

The same idea drawn out, so the method is visible.
Worth knowing: a2+b2=c2a^2 + b^2 = c^2.
Term
Meaning
Example
Row 1 column 1
Row 1 column 2
49=7\sqrt{49} = 7
Row 2 column 1
Row 2 column 2
34×25\frac{3}{4} \times \frac{2}{5}
Row 3 column 1
Row 3 column 2
≈160\approx 160
Row 4 column 1
Row 4 column 2
×10\times 10 moves every digit one column left

Learning

2 boxes
4 steps

How to work with right angled trigonometry

Check the answer against an estimate before you move on, so a place-value slip is caught here.
The layout below is the one the mark scheme expects.

Diagram showing right angled trigonometry laid out step by step

The same idea drawn out, so the method is visible.
  1. Read the question and write down what is being asked for.
  2. Set out the working for right angled trigonometry in the order the method gives.
  3. Substitute the values and simplify.
  4. Check the answer against an estimate before writing it down.
Start from the definition and substitute the numbers the question gives you.
Simplify one line at a time: a2+b2=c2a^2 + b^2 = c^2.
Answer: ≈160\approx 160
2 rules

Key facts: Right angled trigonometry

Work through the method one line at a time and write down what changes at each step.
The layout below is the one the mark scheme expects.

Diagram showing right angled trigonometry laid out step by step

The same idea drawn out, so the method is visible.

  • Rule 1

    How right angled trigonometry behaves in the 1st of the cases the specification names.
    34×25\frac{3}{4} \times \frac{2}{5}

  • Rule 2

    How right angled trigonometry behaves in the 2nd of the cases the specification names.
    ×10\times 10 moves every digit one column left

  • Rule 3

    How right angled trigonometry behaves in the 3rd of the cases the specification names.
    a2+b2=c2a^2 + b^2 = c^2

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Examples

2 boxes
4 marks · worked

Worked example: right angled trigonometry

Sketch the shape even when the question does not ask for one — it makes the next step obvious.
Worth knowing: a2+b2=c2a^2 + b^2 = c^2.
3 marks · worked

Practice question 6: a2+b2=c2a^2 + b^2 = c^2

Sketch the shape even when the question does not ask for one — it makes the next step obvious.

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Common questions

How many marks is right angled trigonometry usually worth?
Between one and four, depending on how many steps the question asks for.
Is this on the A Level Law Edexcel Higher paper?
Yes — it sits in the Writing and structure strand.