Mathematics for Teaching Calculus Differentiation problem in parametric context with solution

## Differentiation problem in parametric context with solution

This is hot off the press-a question taken from the recently concluded 2011 September Preliminary Examinations of a school in Singapore. It deals with applications of differentiation in the parametric context. Extensive trigonometry is employed here together with the manipulation of surd forms. I have personally worked out everything for your (the student’s) reference.

If you want a real calculus challenge, the problem below should satisfy your appetite. Peace.

QUESTION :

The parametric equations of a curve  are

$x = sin2t$ and $y= a cos t$

where is a positive constant $\frac{-\pi}{2} \le t \le\frac{\pi}{2}$

(i) Find the equation of the tangent to the curve at the point P  where $t= \frac{\pi}{4}$.

(ii) The normal to the curve at the point $Q$ where $t = \frac {\pi}{3}$ intersects the axis at $R$. Find the coordinates of $R$ and hence show that the area enclosed by the normal at $Q$ , the tangent $P$ and the x-axis is

###### Author

Frederick Koh is a teacher residing in Singapore who specialises in teaching the A level maths curriculum. He has accumulated more than a decade of tutoring experience and loves to share his passion for mathematics on his personal site www.whitegroupmaths.com.

Mr Koh is also the author of the post Working with summation.

I have created a GeoGebra applet to visualize Question 1 above.