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Trigonometric Identities and Equations

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Question 91
a.

Show that the equation

cos⁡2x−2sin⁡2x=−5cos⁡x \cos^2 x - 2\sin^2 x = -5\cos x cos2x−2sin2x=−5cosx

can be written as

3cos⁡2x+5cos⁡x−2=0. 3\cos^2 x + 5\cos x - 2 = 0. 3cos2x+5cosx−2=0.
[2]
b.

Hence find all values for x x\,x in the interval 0≤x<360∘0 \leq x < 360^\circ0≤x<360∘. Give your answers to one decimal place.

[4]
Markscheme

Trigonometric Identities and Equations Questions

  1. A Level
  2. /Maths
  3. /Trigonometric Identities and Equations

322 exam-style questions on Edexcel A Level Maths Trigonometric Identities and Equations, covering 10.1 Angles in all four Quadrants, 10.2 Exact Values of Trigonometric Ratios, 10.3 Trigonometric Identities, 10.4 Solving Trigonometric Equations, 10.5 Harder Trigonometric Equations, and 10.6 Equations and Identities. Each one has a worked solution and a mark scheme showing where the marks go.

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