a rope of length 18 m is used to form a sector of a circle of radius 3.5 m on a school field. What is the size of the angle of the sector?​

Step-by-step explanation:

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Perimeter of the sector = 2r + length of arc= 2(3.5)+11= 7+11=18 meters exactly the length of the rope.

Step-by-step explanation:

The perimeter of the sector is equivalent to the length of the rope which is 18 meters

Perimeter of the sector= 2 x radius + length of the arc

But length of arc= radius x central angle in radian

18= 2(3.5)+ 3.5(central angle in radians)

18=7+3.5 (central angle in radians)

18–7=3.5(central angle)

11=3.5(central angle)

central angle =11/3.5=3.14 radians or pi radians

Angle in degrees =pi radians x 360 degrees/2pi radians =pi radians x 180 degrees/pi radians = 180 degrees

Therefore the central angle = 180 degrees because pi radians is half of 2pi radians which is half of 360 degrees

Notes: This sector shape is a semicircle because the central angle is 180 degrees

Check: Length of Arc for semicircle =3.5(pi radians)=11 meters

Perimeter of the sector = 2r + length of arc= 2(3.5)+11= 7+11=18 meters exactly the length of the rope.