Results 1 to 6 of 6

Math Help - Urgent angles

  1. #1
    Newbie
    Joined
    May 2009
    Posts
    3

    Talking Urgent angles

    1.The length of the arc of the sector is 12 pie. Find the length of the radius r.

    2. The area of the sector is 18 pie cm ^2 (squared). Find the length of the radius r.
    Last edited by Apocalypse; May 4th 2009 at 07:39 AM.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Mar 2007
    Posts
    1,240

    Talking

    1) Use the formula they gave you for the arc length s having radius r and subtending angle a: s = ra. Assuming "pie" really means "pi" (or \pi), plug in "12pi" for "s" and "30 degrees" for "a". Solve for "r".

    2) A length cannot have squared units. Did they perhaps actually give you the area of the sector, rather than the length of the arc?

    If so, then use the formula they gave you for the area A of the sector having radius r and subtending angle a: A = (a/2)(r^2). Plug "18pi" in for "A" and "45 degrees" in for "a". Solve for "r".

    If you get stuck, please reply showing how far you have gotten. Thank you!
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    May 2009
    Posts
    3

    Talking

    so would it be for question one 12 pi divided by 30 = r? ----------------------------- i.e ------ s = r x a is 12pi=r x 30

    12 pi /30 = 1.25663706

    Is This Correct ?
    Last edited by Apocalypse; May 4th 2009 at 08:14 AM.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Junior Member bebrave's Avatar
    Joined
    Apr 2009
    Posts
    29
    2)
    A(abc)=18 pi
    18pi=(n.r^2.45)/360
    144=r^2
    r=12
    squared what you mean i dont understand if you mean this..solution this.
    if it is something different so..
    Follow Math Help Forum on Facebook and Google+

  5. #5
    A riddle wrapped in an enigma
    masters's Avatar
    Joined
    Jan 2008
    From
    Big Stone Gap, Virginia
    Posts
    2,551
    Thanks
    11
    Awards
    1
    Quote Originally Posted by Apocalypse View Post
    1.The length of the arc of the sector is 12 pie. Find the length of the radius r.
    Hi Apocalypse,

    We can do this a couple of ways. The general formula for finding an arc length given a central angle and radius is

    s=\theta r, where s = the arc length, \theta= the measure of the central angle in radians, and r = the length of the radius.

    12\pi = \frac{\pi}{6}\cdot r

    Solve for r.

    Another approach would be to determine what part of 360 degrees is 30 degrees. Then multiply that times the circumference to get the arc length of 12 pi.

    \frac{30}{360}\cdot 2 \pi r=12 \pi. You should arrive at the same solution for r.









    Quote Originally Posted by Apocalypse View Post
    2. The area of the sector is 18 pie cm ^2 (squared). Find the length of the radius r.
    For this one, I would find what part of the circle 45 degrees is, and then multiply that times the area of a circle to get the area of the sector. Then, from that equation, solve for r.

    \frac{45}{360}\cdot \pi r^2=18 \pi

    ..
    Follow Math Help Forum on Facebook and Google+

  6. #6
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,621
    Thanks
    426
    Quote Originally Posted by Apocalypse View Post
    so would it be for question one 12 pi divided by 30 = r? ----------------------------- i.e ------ s = r x a is 12pi=r x 30

    12 pi /30 = 1.25663706

    Is This Correct ?
    s = r \cdot \theta is valid for \theta in radians, not degrees.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. principle angles and related acute angles
    Posted in the Trigonometry Forum
    Replies: 4
    Last Post: December 19th 2011, 06:40 AM
  2. Compound Angles or Double Angles?
    Posted in the Trigonometry Forum
    Replies: 8
    Last Post: July 25th 2010, 09:05 AM
  3. Replies: 1
    Last Post: January 7th 2009, 06:07 PM
  4. URGENT!! Proving Statemens about angles
    Posted in the Geometry Forum
    Replies: 2
    Last Post: December 16th 2007, 04:19 PM
  5. Replies: 1
    Last Post: November 14th 2007, 08:30 PM

Search Tags


/mathhelpforum @mathhelpforum