9709 P32 - Jun 2014 - Q6
1878
In the diagram, A is a point on the circumference of a circle with centre O and radius r. A circular arc with centre A meets the circumference at B and C. The angle OAB is equal to x radians. The shaded region is bounded by AB, AC and the circular arc with centre A joining B and C. The perimeter of the shaded region is equal to half the circumference of the circle.
- Show that \(x = \cos^{-1} \left( \frac{\pi}{4 + 4x} \right)\).
- Verify by calculation that x lies between 1 and 1.5.
- Use the iterative formula \(x_{n+1} = \cos^{-1} \left( \frac{\pi}{4 + 4x_n} \right)\) to determine the value of x correct to 2 decimal places. Give the result of each iteration to 4 decimal places.
