« previous next »

Author Question: How to work out the area of a sector when i don't have the radius? (Read 3272 times)

TI

  • Sr. Member
  • ****
  • Posts: 434
on: Oct 4, 2013
i have to find the area of a sector but i have been given only the angle(40degrees) and the arc length(18cm) how do i work it out? I suck at rearranging the formula so i would appreciate if you could show me. thnx


formula1

  • Hero Member
  • *****
  • Posts: 666
Reply #1 on: Oct 4, 2013
To find the Area of Circle Sector: (with central angle theta)>if the angle theta is in degrees, then area = (theta/360) PI r2>if the angle theta is in radians, then area = (theta/2) r2

good luck


Related Topics

Need homework help now?

Ask unlimited questions for free

Ask a Question

sadsdas

  • Newbie
  • *
  • Posts: 10
Reply #2 on: Oct 4, 2013
You know the circumference of a circle is pi times twice the radius.

There are 360 degrees in a circle.

So 40/360 = 18/circumference.

Circumference = 162

Therefore, radius = 81/pi

Area of the circle = pi (81/pi)^2 = 6561/pi

So the area of the sector = (6561/pi) * (40/360) = 729/pi

Which is approximately 232 square centimeters.


xclash

  • Hero Member
  • *****
  • Posts: 681
Reply #3 on: Oct 4, 2013
There are 360 degrees in a circle so 40 degrees has to by 40/360 or 1/0 the actual size of the circle:

Perimeter = 2 * pi * r
18cm = 2 * 1/9 * pi * r
r = 81 / pi

area = pi * r^2
area = pi * (81 / pi)^2 * 40/360


sadsdas

  • Newbie
  • *
  • Posts: 10
Reply #4 on: Oct 4, 2013
to get the radius there is a rule that says r=lenght of arc/angle in rad
so u got convert the 40 degrees into rad 40*pie/180 =2/9pie(rad) ,pie=3.14
so the r=length of arc 18cm divided by 2/9pie = 25.78cm !

so area = 1/2 L*R
              1/2 18 *25.78=232


« previous next »
 

Did you know?

Nearly all drugs pass into human breast milk. How often a drug is taken influences the amount of drug that will pass into the milk. Medications taken 30 to 60 minutes before breastfeeding are likely to be at peak blood levels when the baby is nursing.

Did you know?

More than 34,000 trademarked medication names and more than 10,000 generic medication names are in use in the United States.

Did you know?

Signs and symptoms of a drug overdose include losing consciousness, fever or sweating, breathing problems, abnormal pulse, and changes in skin color.

Did you know?

Disorders that may affect pharmacodynamics include genetic mutations, malnutrition, thyrotoxicosis, myasthenia gravis, Parkinson's disease, and certain forms of insulin-resistant diabetes mellitus.

Did you know?

The first monoclonal antibodies were made exclusively from mouse cells. Some are now fully human, which means they are likely to be safer and may be more effective than older monoclonal antibodies.

Lung cancer. Photograph of part of a lung removed after death. The yellow area is a large tumor and Lung cancer. Photograph of part of a lung removed after death. The yellow area is a large tumor and
Effleurage to the entire area with moderate pressure as a finishing technique. Apply effleurage ... Effleurage to the entire area with moderate pressure as a finishing technique. Apply effleurage ...
Clear the inguinal catchment area. Face the side of the table at recipient’s waist. Place your ... Clear the inguinal catchment area. Face the side of the table at recipient’s waist. Place your ...
A container in the shape of a right circular cylinder with no top has surface area square feet. A container in the shape of a right circular cylinder with no top has surface area square feet.
The radius of the Sun is 6.95 × 108 m. It radiates heat at the rate of 5.32 x 10 The radius of the Sun is 6.95 × 108 m. It radiates heat at the rate of 5.32 x 10
How did muscle work around eyeball? How did muscle work around eyeball?
Video: Endocytosis -Types and Phagocytosis

For a complete list of videos, visit our video library