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3.5 The unit circle and exact valuesIB Maths: Analysis and Approaches HL: Subtopic test

10 questions, 27 marks

IB Maths: Analysis and Approaches HL

3.5 The unit circle and exact values

Total 27 marks

Name

Class

Date

  1. 1
    The point PP lies on the unit circle x2+y2=1x^2+y^2=1 such that the line OPOP, where OO is the origin, makes an angle of 2π3\frac{2\pi}{3} measured anticlockwise from the positive xx-axis.
    (a)
    Write down the exact coordinates of PP.
    [1 mark]
    • A(32, −12)\left(\frac{\sqrt3}{2},\,-\frac12\right)
    • B(−32, 12)\left(-\frac{\sqrt3}{2},\,\frac12\right)
    • C(12, 32)\left(\frac12,\,\frac{\sqrt3}{2}\right)
    • D(−12, 32)\left(-\frac12,\,\frac{\sqrt3}{2}\right)
    (b)
    Find the equation of the line OPOP.
    [1 mark]
    • Ay=3xy=\sqrt3x
    • By=−13xy=-\frac{1}{\sqrt3}x
    • Cy=−3xy=-\sqrt3x
    • Dy=−32xy=-\frac{\sqrt3}{2}x
    (c)
    The point QQ lies on the unit circle such that OQOQ makes an angle of −2π3-\frac{2\pi}{3} with the positive xx-axis. Find the exact distance PQPQ.
    [2 marks]

    Total for question 1: 4 marks

  2. 2
    The angle α\alpha satisfies 0<α<π20<\alpha<\frac{\pi}{2}, with sin⁡α=p\sin\alpha=p and cos⁡α=q\cos\alpha=q.
    (a)
    Find sin⁡(π+α)\sin(\pi+\alpha) in terms of pp or qq.
    [1 mark]
    • App
    • B−p-p
    • Cqq
    • D−q-q
    (b)
    Find sin⁡(π−α)\sin(\pi-\alpha) in terms of pp or qq.
    [1 mark]
    • App
    • B−p-p
    • Cqq
    • D−q-q
    (c)
    Find tan⁡(2π−α)\tan(2\pi-\alpha) in terms of pp and qq.
    [2 marks]

    Total for question 2: 4 marks

  3. 3
    In triangle ABCABC, AB=10AB=10 cm, AC=6AC=6 cm and AB^C=30∘A\hat{B}C=30^\circ. There are two possible triangles that fit this information.
    (a)
    Using a calculator, find the two possible sizes of AC^BA\hat{C}B, and verify that both give a valid triangle.
    [3 marks]
    (b)
    Let BC=xBC=x cm. By using the cosine rule in triangle ABCABC, show that x2−103 x+64=0x^2-10\sqrt3\,x+64=0. Hence find the exact difference between the two possible lengths of BCBC.
    [4 marks]

    Total for question 3: 7 marks

  4. 4
    A Ferris wheel has radius 20 m and its centre is 22 m above the ground. A seat starts level with the centre, on the right-hand side, and the wheel turns anticlockwise. After the wheel has turned through an angle θ\theta radians, the seat is 20cos⁡θ20\cos\theta m to the right of the centre and its height above the ground is h=22+20sin⁡θh=22+20\sin\theta m. (A negative horizontal value means the seat is to the left of the centre.)
    (a)
    (i) Find the exact height of the seat when θ=7π6\theta=\frac{7\pi}{6}.
    (ii) Find the exact horizontal distance of the seat from the centre when
    θ=5π4\theta=\frac{5\pi}{4}, and state whether it is to the left or right of the centre.
    (iii) Find the values of
    θ\theta, for 0≤θ<2π0\le\theta<2\pi, at which the seat is 32 m above the ground.
    [6 marks]
    (b)
    (i) Two seats are fixed at diametrically opposite points of the wheel. Show that the sum of their heights is always 44 m.
    (ii) A seat is
    22+10322+10\sqrt3 m above the ground and to the left of the centre. Find the value of θ\theta, where 0≤θ<2π0\le\theta<2\pi, for this seat, justifying your answer.
    [6 marks]

    Total for question 4: 12 marks

End of questions