Show that the equation
10cosθ=3cosecθ 10 \cos \theta = 3 \operatorname{cosec} \theta 10cosθ=3cosecθcan be written in the form
sin2θ=k \sin 2\theta = k sin2θ=kwhere kkk is a constant to be found.
Hence find the smallest positive solution of the equation
10cosθ=3cosecθ 10 \cos \theta = 3 \operatorname{cosec} \theta 10cosθ=3cosecθgiving your answer, in degrees, to one decimal place.
137 exam-style questions on Edexcel A Level Maths Trigonometry and Modelling, covering 7.1 Addition Formulae, 7.2 Double Angle Formulae, 7.3 Solving Trigonometric Equations, 7.4 Simplifying a cos x +- b sin x, 7.5 Proving Trigonometric Identities, and 7.6 Modelling with Trigonometric Functions. Each one has a worked solution and a mark scheme showing where the marks go.