A mechanical linkage is set at an obtuse angle ϕ\phiϕ. The equilibrium position of the linkage is determined by the equation
(4sinϕ+cosϕ)2+(2sinϕ−2cosϕ)2=10.4 (4 \sin \phi + \cos \phi)^2 + (2 \sin \phi - 2 \cos \phi)^2 = 10.4 (4sinϕ+cosϕ)2+(2sinϕ−2cosϕ)2=10.4Find the exact value of sinϕ\sin \phisinϕ. Fully justify your answer.
26 exam-style questions on Edexcel A Level Maths 7.5 Proving Trigonometric Identities. Each one has a worked solution and a mark scheme showing where the marks go.