Results 1 to 8 of 8

Math Help - Arc

  1. #1
    Member M670's Avatar
    Joined
    Sep 2012
    From
    Montreal
    Posts
    142

    Arc

    The radius of the circle with a central angle of that intercepts an arc with length 9 miles is miles.

    I came up with 2.02 miles
    or 12.7 miles both seem wrong
    but then if the formula is S=r(theta) and I would get 9=r(255) r=9/255 r=.035?
    I am just not sure what to do?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    12,114
    Thanks
    988

    Re: Arc

    s = r\theta is only valid if \theta is in radians
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member M670's Avatar
    Joined
    Sep 2012
    From
    Montreal
    Posts
    142

    Re: Arc

    can't I convert it by multiplying (pi/180)
    So it would be 255(pi/180)= 4.45 radians
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    12,114
    Thanks
    988

    Re: Arc

    yes
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Member M670's Avatar
    Joined
    Sep 2012
    From
    Montreal
    Posts
    142

    Re: Arc

    which would then be 9/4.45=2.02 miles as my radius
    Follow Math Help Forum on Facebook and Google+

  6. #6
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    12,114
    Thanks
    988

    Re: Arc

    Quote Originally Posted by M670 View Post
    which would then be 9/4.45=2.02 miles as my radius
    "seem wrong" now?
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Member M670's Avatar
    Joined
    Sep 2012
    From
    Montreal
    Posts
    142

    Re: Arc

    Quote Originally Posted by skeeter View Post
    "seem wrong" now?
    I really can't see my mistake... in this question
    The process looks good to me, I convert 255 degrees into radians then use the formula to derive 2.02 miles as my radius
    Follow Math Help Forum on Facebook and Google+

  8. #8
    MHF Contributor

    Joined
    Aug 2006
    Posts
    18,962
    Thanks
    1784
    Awards
    1

    Re: Arc

    Quote Originally Posted by M670 View Post
    I really can't see my mistake... in this question
    The process looks good to me, I convert 255 degrees into radians then use the formula to derive 2.02 miles as my radius
    I think people who still use degrees, get what they deserve.
    Let \theta=255\cdot\frac{\pi}{180} then r=\frac{9}{\theta}.
    You should get 2.02220398281467.
    Follow Math Help Forum on Facebook and Google+

Search Tags


/mathhelpforum @mathhelpforum