The equation of a curve is y = tan ½x + 3 sin ½x. The curve has a stationary point M in the interval π < x < 2π. Find the coordinates of M, giving each coordinate correct to 3 significant figures.
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2017). The mark or mark type is shown in brackets.
- [M1] Differentiate to obtain form k₁ sec² ½x + k₂ cos ½x
- [A1] Obtain ½ sec² ½x + ½ cos ½x
- [*M1] Equate first derivative to zero and produce cos³½ x = k₃
- [DM1] Use correct process to find one value of x
- [A1] Obtain x = 4.67
- [A1] Obtain y = 1.12
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