Question

The sector of a circle of radius 5cm subtends an angle of 3π/10 rad at the centre. (all answers to 2 dp)

a) calculate the length of the arc.

b) calculate the area of the sector.

c) calculate the area of the segment in the sector with the angle of 3π/10 rad and a radius of 5cm.​

Answer 1

Explanation:

a.

l=rθ (θ in radians)

l=5×3π/10=3π/2≈3/2×3.14≈3×1.57≈4.71 cm

area of sector=π×5²×3π/10×1/2π=15/4 π=15π/4 cm²

≈15/4 ×3.14

≈15×1.57/4

≈5.8875

≈5.89 cm²

Answer 2

Explanation:

3pi / 10 * 180 / pi = 54 degrees.

The circumference of the circle would be 10 pi. Multiply this by 54/360 to get 1.5pi or 3 pi /2

Area of the circle would be 25 pi. Multiply this by 54/360 to get 3.75 pi or 15pi /4

I'm confused on part (c), is it not just the same question as part (b)?

All these answers are assuming that 3pi/10 is the central angle. If it is an inscribed angle, then the central angle would be 6pi/10 or 3pi/5.

Edit: if part (c) is talking about inscribed angle, then the degrees would be 108. Then you just multiply 25pi by 108/360 for your answer