Results 1 to 8 of 8

Math Help - find missing angle?

  1. #1
    Super Member
    Joined
    Oct 2008
    From
    Bristol, England
    Posts
    897

    find missing angle?

    hi, i need to find the missing angle from this shape:

    find missing angle?-shape.jpg

    im not really sure how to do this so if someone could tell me i will be very grateful!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    -1
    e^(i*pi)'s Avatar
    Joined
    Feb 2009
    From
    West Midlands, England
    Posts
    3,053
    Thanks
    1
    Have you covered the cosine rule?

    c^2=a^2+b^2-2ab\cos C which may also be written as \cos C = \dfrac{a^2+b^2-c^2}{2ab}


    Edit: Misread angle as a side - use the law of sines instead (post left here for continuity)
    Last edited by e^(i*pi); January 17th 2011 at 08:52 AM.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Super Member
    Joined
    Oct 2008
    From
    Bristol, England
    Posts
    897
    would c^2= 6, a^2= 10 and b^2= 96??
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,701
    Thanks
    454
    Law of sines ...

    \displaystyle \frac{\sin(96^\circ)}{10} = \frac{\sin{\theta}}{6}<br />

    solve for \theta


    Follow Math Help Forum on Facebook and Google+

  5. #5
    -1
    e^(i*pi)'s Avatar
    Joined
    Feb 2009
    From
    West Midlands, England
    Posts
    3,053
    Thanks
    1
    Quote Originally Posted by andyboy179 View Post
    would c^2= 6, a^2= 10 and b^2= 96??
    My apologies, I misread that angle as a side. Instead you can use the sine rule

    \dfrac{\sin A}{a} = \dfrac{\sin B}{b}

    In this case you have
    • a = 6
    • \sin B = 96
    • b = 10


    \sin A = \dfrac{a \sin B}{b} = \dfrac{6 \sin(96)}{10}
    Last edited by e^(i*pi); January 17th 2011 at 10:45 AM. Reason: latex
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Super Member
    Joined
    Oct 2008
    From
    Bristol, England
    Posts
    897
    would i start it like this?

    find missing angle?-untitled.jpg
    Follow Math Help Forum on Facebook and Google+

  7. #7
    -1
    e^(i*pi)'s Avatar
    Joined
    Feb 2009
    From
    West Midlands, England
    Posts
    3,053
    Thanks
    1
    Yes, that's fine.

    Me and skeeter used the other way of writing it which is the same as you but flipped over. I have started it off in post 6
    Follow Math Help Forum on Facebook and Google+

  8. #8
    Super Member
    Joined
    Oct 2008
    From
    Bristol, England
    Posts
    897
    would i then do sin?= 6x10/sin96=60.33?
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. missing angle
    Posted in the Trigonometry Forum
    Replies: 9
    Last Post: February 28th 2011, 07:06 PM
  2. missing angle
    Posted in the Trigonometry Forum
    Replies: 6
    Last Post: January 31st 2011, 06:59 AM
  3. find missing angle?
    Posted in the Geometry Forum
    Replies: 4
    Last Post: January 24th 2011, 08:55 AM
  4. work out missing angle?
    Posted in the Geometry Forum
    Replies: 52
    Last Post: December 17th 2010, 04:32 AM
  5. missing angle
    Posted in the Geometry Forum
    Replies: 1
    Last Post: April 12th 2008, 05:34 PM

Search Tags


/mathhelpforum @mathhelpforum