CAIE P2 2015 November — Question 3 6 marks

Exam BoardCAIE
ModuleP2 (Pure Mathematics 2)
Year2015
SessionNovember
Marks6
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicParametric differentiation
TypeFind tangent equation at parameter
DifficultyModerate -0.3 This is a straightforward parametric differentiation question requiring standard techniques: find dx/dt and dy/dt, compute dy/dx = (dy/dt)/(dx/dt), evaluate at t=0 to get the gradient, find the point on the curve at t=0, then write the tangent equation. While it involves the product rule and chain rule, these are routine A-level skills with no conceptual challenges or novel problem-solving required.
Spec1.03g Parametric equations: of curves and conversion to cartesian1.07s Parametric and implicit differentiation

3 The parametric equations of a curve are $$x = ( t + 1 ) \mathrm { e } ^ { t } , \quad y = 6 ( t + 4 ) ^ { \frac { 1 } { 2 } }$$ Find the equation of the tangent to the curve when \(t = 0\), giving the answer in the form \(a x + b y + c = 0\) where \(a , b\) and \(c\) are integers.

Question 3:
AnswerMarks Guidance
Answer/WorkingMark Guidance
Obtain \(\frac{\mathrm{d}x}{\mathrm{d}t}=e^t+(t+1)e^t\) or equivalentB1
Obtain \(\frac{\mathrm{d}y}{\mathrm{d}t}=t(t+4)^{-\frac{1}{2}}\)B1
Substitute \(t=0\) and divide to obtain gradient of tangentM1
Obtain \(\frac{3}{4}\) following their first derivativesA1
Form equation of tangent through \((1,12)\)M1
Obtain \(3x-4y+45=0\) or equivalent of required formA1 [6]
## Question 3:

| Answer/Working | Mark | Guidance |
|---|---|---|
| Obtain $\frac{\mathrm{d}x}{\mathrm{d}t}=e^t+(t+1)e^t$ or equivalent | B1 | |
| Obtain $\frac{\mathrm{d}y}{\mathrm{d}t}=t(t+4)^{-\frac{1}{2}}$ | B1 | |
| Substitute $t=0$ and divide to obtain gradient of tangent | M1 | |
| Obtain $\frac{3}{4}$ following their first derivatives | A1 | |
| Form equation of tangent through $(1,12)$ | M1 | |
| Obtain $3x-4y+45=0$ or equivalent of required form | A1 | [6] |

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3 The parametric equations of a curve are

$$x = ( t + 1 ) \mathrm { e } ^ { t } , \quad y = 6 ( t + 4 ) ^ { \frac { 1 } { 2 } }$$

Find the equation of the tangent to the curve when $t = 0$, giving the answer in the form $a x + b y + c = 0$ where $a , b$ and $c$ are integers.

\hfill \mbox{\textit{CAIE P2 2015 Q3 [6]}}