OCR Further Pure Core 2 2020 November — Question 6

Exam BoardOCR
ModuleFurther Pure Core 2 (Further Pure Core 2)
Year2020
SessionNovember
TopicPolar coordinates

6 The equation of a curve in polar coordinates is \(r = \ln ( 1 + \sin \theta )\) for \(\alpha \leqslant \theta \leqslant \beta\) where \(\alpha\) and \(\beta\) are non-negative angles. The curve consists of a single closed loop through the pole.
  1. By solving the equation \(r = 0\), determine the smallest possible values of \(\alpha\) and \(\beta\).
  2. Find the area enclosed by the curve, giving your answer to 4 significant figures.
  3. Hence, by considering the value of \(r\) at \(\theta = \frac { \alpha + \beta } { 2 }\), show that the loop is not circular.