Radian Measure: Arc Length and Sector Area

Radian Measure: Arc Length and Sector Area

Secondary 3

In the diagram below, \(APB\) is an arc of a circle centre \(O\) and radius \(5\) cm.
\(AQB\) is semicircle with \(AB\) as its diameter and \(\angle AOB = \frac{4}{9}\pi\).

  1. Show that the length of \(AB = 6.43\) cm.
  2. Calculate the length of the arc \(APB\).
  3. Calculate the area of the semi-circle \(AQB\).
  4. Calculate the area of the \(\Delta AOB\) and hence, find the area of shaded region.

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Answer:(i) \(AB=6.43\text{ cm}\) (ii) \(6.98\text{ cm}\) (iii) \(16.2\text{ cm}^2\) (iv) Triangle \(AOB\): \(12.3\text{ cm}^2\) Shaded region: \(11.1\text{ cm}^2\)

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