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Jetzt kostenlos anmeldenA sector of a circle is an area of a circle where two of the sides are radii. An example of the sector (in red) is shown below:
An arc length is a part of the circle's circumference (perimeter). For the same sector, we could have arc as shown in green:
You might already be familiar with this but let's look at calculating the area and arc length of a circle sector when the angle is given in degrees.
The formula to calculate the area of a sector with an angle \(\theta\) is:
\(\text{Area of a sector} = \pi \cdot r^2 \cdot \frac{\theta}{360}\)
where r is the radius of the circle
Circle A has a diameter of 10cm. A sector of circle A an angle of 50. What is the area of this sector?
\(\text{diameter = radius} \cdot 2\)
\(\text{radius} = \frac{\text{diameter}}{2} = \frac{10}{2} = 5 \space cm\)
The formula to calculate the arc length of a sector with an angle \(\theta\) is:
\(\text{Arc Length of a sector}: \pi \cdot d \cdot \frac{\theta}{360}\) where d is the diameter of the circle:
Circle B has a radius of 12cm. A sector within Circle B has an angle of 100. What is the length of the arc length of this sector?
Degrees | Radians |
\(\frac{\pi}{6}\) | |
\(\frac{\pi}{4}\) | |
\(\frac{\pi}{3}\) | |
\(\frac{\pi}{2}\) | |
\(\pi\) | |
\(\frac{3\pi}{2}\) | |
\(2 \pi\) |
To calculate the area of a sector of a circle with an angle \(\theta^r\), the formula you use is:
\(\text{Area of a sector} = \frac{1}{2} \cdot r^2 \cdot \theta\)
where r is the radius of the circle.
Circle C has a radius of 15cm. Within Circle C, there is a sector with an angle of 0.5 radians. What is the area of this sector?
To calculate the arc length of a sector of a circle with an angle \(\theta^r\), the formula you use is:
\(\text{Arc length of a sector} = r \cdot \theta\), where r is the radius of the circle.
A sector in Circle D has an angle of 1.2 radians. Circle D has a diameter of 19. What is the arc length of this sector?
\(\text{Diameter = Radius} \cdot 2\text{ Radius} = \frac{\text{Diameter}}{2} = \frac{19}{2} = 9.5\)
\(\text{Arc Length of a sector} = \pi \cdot d \cdot \frac{\theta}{360}\)
A sector of a circle is a proportion of a circle where two sides are radii.
To find the sector of a circle you need to use one of the formulas for the area of the sector. Which one you use is dependent on whether the angle at the centre is in radians or in degrees.
There are two formulas of a sector. One is to calculate the area of a sector of a circle. Area of a sector= pi × r^2 × (θ /360). The other one is to find the arc length of the sector of the circle. Arc length = pi × d × (θ /360)
What is a sector?
A sector of a circle is a proportion of a circle where two slides are radii
How do you find the sector of a circle?
To find the sector of a circle you need to use one of the formulas for the area of the sector. Which one you use is dependent on whether the angle at the centre is in radians or in degrees
There are two formulas to find the area of a sector of a circle. What decides which one you use?
Whether the angle at the centre of the circle is in degrees or radians
What is an arc length?
A proportion of the circle’s circumference, which is defined by the sector.
Circle A has a diameter of 10cm. A sector of circle A has an angle of 120. What is the area of this sector?
105 (3 s.f)
Circle B has a diameter of 4cm. A sector of circle B has an angle of 20. What is the area of this sector?
2.79 (3 s.f)
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