1. **Problem statement:**
Given a circle with center O and radius 8 m, points P, Q, and R lie on the circumference. OPQ is a straight line, \(\angle QOR = 36.9^\circ\), and OR is perpendicular to QR. We need to find:
(i) the arc length PR,
(ii) the perimeter of the shaded region PQR.
2. **Relevant formulas and rules:**
- Arc length \(s = r\theta\) where \(r\) is radius and \(\theta\) is the central angle in radians.
- Perimeter of shaded region PQR = length of arc PR + length of PQ + length of QR.
- Since OPQ is a straight line, \(\angle POQ = 180^\circ\).
- OR is perpendicular to QR means \(\angle ORQ = 90^\circ\).
3. **Find the central angle \(\angle POR\):**
Since \(\angle QOR = 36.9^\circ\) and OPQ is a straight line, \(\angle POQ = 180^\circ\).
Therefore, \(\angle POR = \angle POQ - \angle QOR = 180^\circ - 36.9^\circ = 143.1^\circ\).
4. **Calculate arc length PR:**
Convert \(\angle POR\) to radians:
$$\theta = 143.1^\circ \times \frac{\pi}{180} = \frac{143.1\pi}{180}$$
Arc length:
$$s = r\theta = 8 \times \frac{143.1\pi}{180} = \frac{1144.8\pi}{180} = \frac{1144.8\pi}{180}$$
Simplify fraction:
$$\frac{1144.8}{180} = 6.36$$
So,
$$s = 6.36\pi \approx 19.97\text{ m}$$
5. **Find lengths PQ and QR:**
- Since OPQ is a straight line and O is center, P and Q lie on the circle with radius 8 m.
- Length PQ = OP + OQ = 8 + 8 = 16 m.
- To find QR, use right triangle ORQ where OR = 8 m (radius), and \(\angle ORQ = 90^\circ\).
- \(\angle QOR = 36.9^\circ\) is the angle at O between Q and R.
Using triangle ORQ:
- QR is opposite to \(\angle QOR = 36.9^\circ\), OR is adjacent.
Calculate QR:
$$QR = OR \times \tan(36.9^\circ) = 8 \times \tan(36.9^\circ)$$
Calculate \(\tan(36.9^\circ)\): approximately 0.75
So,
$$QR = 8 \times 0.75 = 6\text{ m}$$
6. **Calculate perimeter of shaded region PQR:**
$$\text{Perimeter} = \text{arc length PR} + PQ + QR = 19.97 + 16 + 6 = 41.97\text{ m}$$
**Final answers:**
(i) Arc length PR \(\approx 19.97\) m
(ii) Perimeter of shaded region PQR \(\approx 41.97\) m
Circle Arc Perimeter C83Ad7
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