2023 SJI P2 Q9

2023 SJI P2 Q9

IB Year 5 | Grade 11
21 marks

Consider \(\mathrm f(x)=\ln\left(\dfrac{\sqrt{x^2-1}}{\mathrm e}\right)\), \(x\in D\).

  1. Find the largest possible domain \(D\) for \(\mathrm f\) to be a function.[2]
  2. Sketch the graph of \(y=\mathrm f(x)\). Label clearly the equations of the asymptotes and the coordinates of any intercepts with the axes.[3]
  3. Determine whether the inverse function \(\mathrm f^{-1}\) exists.[2]

The function \(\mathrm g\) is defined by \(\mathrm g(x)=\ln\left(\dfrac{\sqrt{x^2-1}}{\mathrm e}\right)\), \(x\in(1,\infty)\).

  1. Find the inverse function \(\mathrm g^{-1}\) and state its domain.[5]
  2. State the rule and domain of the composite function \(\mathrm g^{-1}\circ\mathrm f\).[2]
  3. Find \(\mathrm g'(x)\).[3]
  4. Solve \(\mathrm g'(x)=0\).[2]
  5. Prove that there are no solutions to \(\dfrac{\mathrm d}{\mathrm dx}(\mathrm g^{-1}(x))=0\).[2]

Solution:

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Answer:(a) \(x<-1\) or \(x>1\) (b) Asymptotes \(x=\pm1\), intercepts \((\pm\sqrt{\mathrm e^2+1},0)\) (c) Does not exist (d) \(\sqrt{\mathrm e^{2x+2}+1},\ x\in\mathbb R\) (e) \(|x|,\ x<-1\text{ or}\hspace{0.5em}x>1\) (f) \(x/(x^2-1)\) (g),(h) No solutions.

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