Solve the equation

Mark scheme

Marking points from the official mark scheme (May/June 2017). The mark or mark type is shown in brackets.

1. [M1] implied by 0.848[06...]
2. [M1] implied by a correct answer of acceptable accuracy
3. [A1] 0.544 486... rot to 3 or more figs isw
4. [A1] 1.03 or 1.02630... rot to 4 or more figs isw
5. [A1] Maximum 3 marks if extra angles in range; no penalty for extra values outside range 0≤x≤π/2
6. [M1] Correctly uses tan² y = sec² y-1 and/or siny/cosy and sin² y=1-cos² y for using correct relationship(s) to find an equation in terms of a single trigonometric ratio
7. [DM1] 3 sec² y – 14 sec y – 5 = 0 => (3secy +1)(secy – 5) or 5cos² y + 14 cos y – 3 = 0 => (5cos y-1)(cos y + 3) for factorising or solving their 3-term quadratic dependent on the first M1 being awarded
8. [A1] [cos y = -3] cos y = 1/5
9. [A1] 78.5 or 78.4630... rot to 2 or more decimal places isw
10. [A1] 281.5 or 281.536.... rot to 2 or more decimal places isw
11. [A1] Maximum 4 marks if extra angles in range; no penalty for extra values outside range 0≤x≤360