Results 1 to 5 of 5

Math Help - finding area of a circular sector

  1. #1
    Newbie
    Joined
    Feb 2010
    Posts
    12

    finding area of a circular sector

    Hello all! I just found this site and was hoping I could get some Trig help.

    Could you please check my work?

    given r=9cm and theta=120deg

    A=1/2(r^2)(/theta)

    1/2(9cm)^2(120/360)

    1/2(81cm^2)(120/360)

    (40.5cm^2)(120/360)

    A=13.5cm^2

    Thanks for taking a look!

    Joe
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Banned
    Joined
    Feb 2010
    Posts
    66
    Not quite. Change 120 degrees into radians, and don't divide by 360. I think you are still thinking in terms of the sector being a ratio [fraction] of the entire circle, but that was done in developing the formula in the first place. Once you have the formula, and you do, just plug and chug, but DO use radians, not degrees.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Feb 2010
    Posts
    12
    A=1/2(r^2)(/theta)

    1/2(9cm)^2(120pi/180)

    1/2(81cm^2)(2pi/3)

    (40.5cm^2)(2pi/3) <------ this is where I get stuck. Am I supposed to convert this to decimal form?

    (40.5cm^2)(.1960)

    A=7.9398cm^2
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by rasczak View Post
    A=1/2(r^2)(/theta)

    1/2(9cm)^2(120pi/180)

    1/2(81cm^2)(2pi/3)

    (40.5cm^2)(2pi/3) <------ this is where I get stuck. Am I supposed to convert this to decimal form? Mr F says: It depends on whether the question requires an exact answer or an approximate answer. Note that this answer can be further simplified.

    (40.5cm^2)(.1960)

    A=7.9398cm^2
    ..
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Feb 2010
    Posts
    12
    Quote Originally Posted by mr fantastic View Post
    ..
    The original question was

    a.) Find the length of the arc of the colored sector
    b.) Find the area of the sector.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Finding radius of a circular sector.
    Posted in the Trigonometry Forum
    Replies: 3
    Last Post: September 11th 2011, 09:39 PM
  2. circle incribed in a circular sector
    Posted in the Trigonometry Forum
    Replies: 2
    Last Post: August 24th 2011, 07:29 PM
  3. Finding area of a sector
    Posted in the Geometry Forum
    Replies: 3
    Last Post: April 26th 2011, 02:31 AM
  4. Replies: 3
    Last Post: January 2nd 2010, 04:36 AM
  5. area of a sector
    Posted in the Geometry Forum
    Replies: 2
    Last Post: September 23rd 2008, 02:41 PM

Search Tags


/mathhelpforum @mathhelpforum