QCEVault

Proof and induction — Question 22

Original QCE Vault practice · 6 marks

Q22 · Practice questionComplex familiar6 marks

QUESTION 22 (6 marks)

a)
Use De Moivre’s theorem to prove cos⁡4x=8cos⁡4x−8cos⁡2x+1.\cos4x=8\cos^4x-8\cos^2x+1.
[4 marks]
b)
Hence solve cos⁡4x=0\cos4x=0 for 0≤x≤π/20\le x\le\pi/2.
[2 marks]
Question linkSyllabus coverage

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