Results 1 to 3 of 3

Math Help - geometry of circle

  1. #1
    Member Rimas's Avatar
    Joined
    Sep 2006
    From
    West Philly
    Posts
    86

    geometry of circle

    If the area of a disc insribed in a square is 36 pie cm ^2 what is the area of the square
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Global Moderator

    Joined
    Nov 2005
    From
    New York City
    Posts
    10,616
    Thanks
    9
    Quote Originally Posted by Rimas View Post
    If the area of a disc insribed in a square is 36 pie cm ^2 what is the area of the square
    Okay is the diamter of the disk?

    We know that,
    \pi r^2=36
    Thus,
    r^2=\frac{36}{\pi}\approx 11.5
    Thus,
    r=\sqrt{11.5}\approx 3.39 \mbox{ cm}
    That means the diamter of the circle is twice as much,
    d\approx 6.77 \mbox{ cm}
    But the diamter of the circle is the hypotenuse of the square.

    The square creates a 45,45,90 triangle. Thus, the side of the square is,
    s=\frac{6.77}{\sqrt{2}}\approx 4.79 \mbox{ cm}
    That means the area of the square is,
    A=s^2\approx 22.93 \mbox{ cm}^2
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    Quote Originally Posted by Rimas View Post
    If the area of a disc insribed in a square is 36 pie cm ^2 what is the area of the square
    See diagram.

    Now let r be the radius of the circle then:

    36 pi = pi r^2,

    and so r=6 cm.

    Therefore the side of the square is 12 cm, and its area is
    144 sq cm.

    RonL
    Attached Thumbnails Attached Thumbnails geometry of circle-gash.jpg  
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 6
    Last Post: July 8th 2010, 05:39 PM
  2. Circle Geometry: Centre of Circle
    Posted in the Geometry Forum
    Replies: 1
    Last Post: July 8th 2010, 06:44 AM
  3. Circle Geometry
    Posted in the Geometry Forum
    Replies: 1
    Last Post: May 19th 2009, 03:08 AM
  4. Circle Geometry
    Posted in the Geometry Forum
    Replies: 4
    Last Post: October 11th 2008, 03:21 AM
  5. circle geometry
    Posted in the Geometry Forum
    Replies: 0
    Last Post: September 3rd 2008, 12:12 PM

Search Tags


/mathhelpforum @mathhelpforum