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Strategy for Trigonometric Equations (Edexcel A Level Maths): Revision Note

Lucy Kirkham

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Strategy for Trigonometric Equations

How to approach solving trig equations

  • You can solve trig equations in a variety of different ways

    • Sketching a graph (see Graphs of Trigonometric Functions)

    • Using trigonometric identities (see Trigonometry – Simple Identities)

    • Using the CAST diagram (see Linear Trigonometric Equations)

    • Factorising quadratic trig equations (see Quadratic Trigonometric Equations)

  • You may be asked to use degrees or radians to solve trigonometric equations

    • Make sure your calculator is in the correct mode

    • Remember common angles

      • 90° is ½π radians

      • 180° is π radians

      • 270° is 3π/2 radians

      • 360° is 2π radians 

  • If you’re having trouble solving a trig equation, this flowchart might help:

 

Strategy for Trigonometric Equations Diagram 1, A Level & AS Level Pure Maths Revision Notes

Examiner Tips and Tricks

  • Don’t forget to check the function range and ensure you have included all possible solutions.

  • If the question involves a function of x or θ, make sure you transform the range first (and ensure you transform your solutions back again at the end!). 

Worked Example

Strategy for Trigonometric Equations Example Solution, A Level & AS Level Pure Maths Revision Notes

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    Lucy Kirkham

    Author: Lucy Kirkham

    Expertise: Head of STEM

    Lucy has been a passionate Maths teacher for over 12 years, teaching maths across the UK and abroad helping to engage, interest and develop confidence in the subject at all levels.Working as a Head of Department and then Director of Maths, Lucy has advised schools and academy trusts in both Scotland and the East Midlands, where her role was to support and coach teachers to improve Maths teaching for all.