3.4.4 Strategy for Trigonometric Equations
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:
Exam Tip
- 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
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