Strategy for Trigonometric Equations (Cambridge (CIE) AS Maths): Revision Note
Exam code: 9709
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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:
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
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