Sine curve with a vertical shift: constant, transformations, sketch, inequality and number of roots

Sine curve with a vertical shift: constant, transformations, sketch, inequality and number of roots

IB Year 6 | Grade 12
10 marks

The function \(\mathrm{f}\) is defined by \(\mathrm{f}(x)=q-2\sin3x\) for \(0\le x\le\pi\), where \(q\) is a constant.

  1. The least value of \(\mathrm{f}(x)\) is \(-1\). Find \(q\) and write down the range of \(\mathrm{f}\).[2]
  2. Describe fully a sequence of transformations that maps the graph of \(y=\sin x\) onto the graph of \(y=\mathrm{f}(x)\).[2]
  3. On the grid below, sketch the graph of \(y=\mathrm{f}(x)\).[2]
  4. Solve the inequality \(\mathrm{f}(x)<0\).[2]
  5. Find the set of values of \(k\) for which the equation \(\mathrm{f}(x)=k\) has
    1. exactly one solution,
    2. exactly four solutions.[2]

Solution:

Solution locked

680+ questions here come with free worked solutions. A free account saves your questions and progress; this one needs tuition enrolment.

Create a free account to practise similar questions.

Answer:(a) \(q=1\), range \(-1\le\mathrm{f}(x)\le3\) (b) stretch parallel to the \(x\)-axis, scale factor \(\dfrac13\); stretch parallel to the \(y\)-axis, scale factor \(2\), with reflection in the \(x\)-axis; translation \(1\) unit in the positive \(y\)-direction (d) \(\dfrac{\pi}{18}<x<\dfrac{5\pi}{18}\) or \(\dfrac{13\pi}{18}<x<\dfrac{17\pi}{18}\) (e)(i) \(k=3\) (e)(ii) \(-1<k\le1\)

Need help? Join our JC Math tuition classes.

Learn more