Exponential curve with a tangent and the coordinate axes

Exponential curve with a tangent and the coordinate axes

Secondary 4
11 marks
Original parallel to supplied A Math Applications of Integration references

The curve \(y=5-\mathrm{e}^{x}\) has a tangent at \(A\), where the \(x\)-coordinate of \(A\) is \(\ln2\). The tangent meets the \(y\)-axis at \(B\), and the curve meets the \(x\)-axis at \(C\).

  1. Find the equation of the tangent at \(A\).[3]
  2. Find the coordinates of \(B\) and \(C\).[3]
  3. Hence find the exact area of the shaded region bounded by the curve, the tangent and the coordinate axes.[5]

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Answer:(i) \(y=-2x+3+2\ln2\) (ii) \(B=(0,3+2\ln2)\), \(C=(\ln5,0)\) (iii) \((\ln2)^2+5\ln5-2\ln2-3\text{ units}^2\)

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