Strategy for Trigonometric Equations (Edexcel IAL Maths)

Spec point — 6.2

Strategy for trigonometric equations

What strategies can I use for solving trigonometric 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:

Exam Hint

• 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