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Date May 2021 Marks available 5 Reference code 21M.1.SL.TZ1.13
Level Standard Level Paper Paper 1 Time zone Time zone 1
Command term Find Question number 13 Adapted from N/A

Question

Sieun hits golf balls into the air. Each time she hits a ball she records θ, the angle at which the ball is launched into the air, and l, the horizontal distance, in metres, which the ball travels from the point of contact to the first time it lands. The diagram below represents this information.

Sieun analyses her results and concludes:

dldθ=-0.2θ+9,  35°θ75°.

Determine whether the graph of l against θ is increasing or decreasing at θ=50°.

[3]
a.

Sieun observes that when the angle is 40°, the ball will travel a horizontal distance of 205.5m.

Find an expression for the function lθ.

[5]
b.

Markscheme

l'50=-0.2×50+9            (M1)

=-1            A1

the curve is decreasing at θ=50°            A1


Note: For the final A1, follow through within this question part for their l'50 value. Award A0 for an answer of "decreasing" with no work shown.


[3 marks]

a.

recognition of need to integrate (e.g. reverse power rule or integral symbol or integrating at least one term correctly)            (M1)

lθ=-0.1θ2+9θ+c            A1A1

205.5=-0.1×402+9×40+c        (M1)


Note: Award M1 for correct substitution of θ=40° and l=205.5. A constant of integration must be seen (can be implied by a correct answer).


c=5.5

lθ=-0.1θ2+9θ+5.5            A1


Note: Accept any variable in the working, but for the final A1, the variable θ must be used in the expression.


[5 marks]

b.

Examiners report

[N/A]
a.
[N/A]
b.

Syllabus sections

Topic 5—Calculus » SL 5.2—Increasing and decreasing functions
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