A-LevelMathematicsTrigonometry9709/21 · Oct/Nov 2018 · Q35 Marks
Solve the equation sec² θ = 3 cosec θ for 0° < θ < 180°.
- (a)Solve the equation sec² θ = 3 cosec θ for 0° < θ < 180°.[5]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2018). The mark or mark type is shown in brackets.
- [B1] State 1/cos²θ = 3/sinθ or 1+tan²θ = 3/sinθ
- [M1] Produce quadratic equation in sinθ Dependent on B1
- [M1] Solve 3-term quadratic equation to find value between –1 and 1 for sinθ Dependent on first M1
- [A1] Obtain sinθ = ½(-1+√37) and hence 57.9
- [A1] Obtain 122.1 and no others between 0 and 180
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