Consider 6cos2x=4−sinx6\cos^2x=4-\sin x6cos2x=4−sinx.
Show that this becomes 6sin2x−sinx−2=06\sin^2x-\sin x-2=06sin2x−sinx−2=0.
Hence solve for 0∘≤x<360∘0^\circ\leq x<360^\circ0∘≤x<360∘.
42 exam-style questions on CCEA A Level Maths 1.4.6 Trigonometry. Each one has a worked solution and a mark scheme showing where the marks go.