Show that cos3θ≡4cos3θ−3cosθ\cos 3\theta \equiv 4\cos^3\theta - 3\cos\thetacos3θ≡4cos3θ−3cosθ.
Hence solve, for −π≤x≤π-\pi \leq x \leq \pi−π≤x≤π, the equation
1−cos3x=sin2x1 - \cos 3x = \sin^2 x1−cos3x=sin2x
Give your answers to three significant figures where they are not exact.
221 exam-style questions on CCEA A Level Maths 3.4 Trigonometry (A-level only), covering 3.4.1 Trigonometry (A-level only), 3.4.2 Trigonometry (A-level only), 3.4.3 Trigonometry (A-level only), 3.4.4 Trigonometry (A-level only), 3.4.5 Trigonometry (A-level only), 3.4.6 Trigonometry (A-level only), 3.4.7 Trigonometry (A-level only), and 3.4.8 Trigonometry (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.