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# Add Math(F4) Circular Measure 8.3

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### Transcript

• 1. SUBTOPIC 8.3: AREA OF SECTOR OF A CIRCLE CHAPTER 8: CIRCULAR MEASURE
• 2. The net of a cone consists of a circle and a sector.
• 3. Area of sector OPQR Area of circle AREA OF A SECTOR The area of a sector, A is proportional to the angle subtended at the centre of the circle. θ rad Q
• 4. Therefore, The area of sector of a circle is; When using the formula , remember that the angle θ is measured in radians.
• 5. Example 1
• Calculate the area of the shaded sector of a circle of radius 5 cm. Given that the circle subtends an angle of 1.4 rad at the centre.
• 6. Solution Area of the shaded sector
• 7. Example 2
• Given the area of the shaded sector of a circle is 64 cm 2 and the angle subtended at the centre is 120º. Calculate the radius of the circle.
120 º
• 8. Solution Area of the shaded sector 120º = 2.094 rad
• 9. Example 3
• Given that the area of the shaded sector of a circle is 80 cm 2 and the radius is 6.5 cm. Find the central angle, θ , in radian.
θ
• 10. Solution Area of the sector
• 11. WORKSHEET
• 12.
• Given a circle with centre O and
• radius 14 cm. The minor arc AB subtends an angle of 65º at the
• centre of the circle. Calculate the
• area of the minor sector subtended by the arc AB .
• 13.
• 2. Complete the table below, given the areas and the radii of the sectors
• and angles subtended.
8 cm 145 cm 2 1.778 rad 200 cm 2 6.5 cm 18л cm 2 θ = 1.64 rad 72 cm 2 50º 38.12 cm 9.15 cm 90 cm 2 Angle subtended, θ Radius, r Area of sector, A
• 14. SUMMARY Circular Measure Л rad = 180º Area of sector, A θ