Results 1 to 14 of 14

Math Help - Working out area

  1. #1
    Senior Member Mukilab's Avatar
    Joined
    Nov 2009
    Posts
    468

    Working out area

    ABC is a triangle

    AB=8cm
    BC=14cm
    Angle ABC=106

    Calculate the area... correct to 3 significant figures.

    Even with splitting it up into right angled triangles doesn't work...
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Master Of Puppets
    pickslides's Avatar
    Joined
    Sep 2008
    From
    Melbourne
    Posts
    5,234
    Thanks
    27
    A = \frac{1}{2}ac\sin(B)

    In your case

    A = \frac{1}{2}\times 14\times 8 \times \sin(106)
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Senior Member Mukilab's Avatar
    Joined
    Nov 2009
    Posts
    468
    Quote Originally Posted by pickslides View Post
    A = \frac{1}{2}ac\sin(B)

    In your case

    A = \frac{1}{2}\times 14\times 8 \times \sin(106)

    Please tell me the resources where you get such knowledge :/

    Thank you though.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Senior Member Mukilab's Avatar
    Joined
    Nov 2009
    Posts
    468
    This calculates to -40...... can't be the area.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Master Of Puppets
    pickslides's Avatar
    Joined
    Sep 2008
    From
    Melbourne
    Posts
    5,234
    Thanks
    27
    Quote Originally Posted by Mukilab View Post
    Please tell me the resources where you get such knowledge :/

    I study notes taken in classes, from books and discussions i have with colleges. The internet is also a great medium for information. Studying is great, you should try it out, it can be very rewarding.
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Master Of Puppets
    pickslides's Avatar
    Joined
    Sep 2008
    From
    Melbourne
    Posts
    5,234
    Thanks
    27
    Quote Originally Posted by Mukilab View Post
    This calculates to -40...... can't be the area.
    \sin(106) > 0 as \forall \theta \in \{0< \theta < 180\} then \sin(\theta) \geq 0 therefore the correct answer must be positive.

    Is your calculator calibrated correctly?
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Senior Member Mukilab's Avatar
    Joined
    Nov 2009
    Posts
    468
    I do study, I just find it hard to locate the correct and adequate resources. I don't know any greek signs apart from theta so if you could explain that in words....
    Follow Math Help Forum on Facebook and Google+

  8. #8
    Master Of Puppets
    pickslides's Avatar
    Joined
    Sep 2008
    From
    Melbourne
    Posts
    5,234
    Thanks
    27
    Quote Originally Posted by pickslides View Post
    \sin(106) > 0 as \forall \theta \in \{0< \theta < 180\} then \sin(\theta) \geq 0 therefore the correct answer must be positive.


    Quote Originally Posted by Mukilab View Post
    I do study, I just find it hard to locate the correct and adequate resources. I don't know any greek signs apart from theta so if you could explain that in words....
    The only greek letter in my statement was theta.

    The statement means that for all angles between 0 and 180 sin will be positive. Therefore the result you are after must be positive as we are taking that postive result and multiplying it by only positive numbers.
    Follow Math Help Forum on Facebook and Google+

  9. #9
    -1
    e^(i*pi)'s Avatar
    Joined
    Feb 2009
    From
    West Midlands, England
    Posts
    3,053
    Thanks
    1
    Quote Originally Posted by Mukilab View Post
    ABC is a triangle

    AB=8cm
    BC=14cm
    Angle ABC=106

    Calculate the area... correct to 3 significant figures.

    Even with splitting it up into right angled triangles doesn't work...
    Using pickslide's method I get 58.8 as an answer
    Follow Math Help Forum on Facebook and Google+

  10. #10
    Senior Member Mukilab's Avatar
    Joined
    Nov 2009
    Posts
    468
    Pickleslides, what does the upside down A mean than?
    Follow Math Help Forum on Facebook and Google+

  11. #11
    Master Of Puppets
    pickslides's Avatar
    Joined
    Sep 2008
    From
    Melbourne
    Posts
    5,234
    Thanks
    27
    Quote Originally Posted by Mukilab View Post
    Pickleslides, what does the upside down A mean than?
    It means "for all"

    As in for all numbers in a certain set or over an interval.
    Follow Math Help Forum on Facebook and Google+

  12. #12
    Senior Member Mukilab's Avatar
    Joined
    Nov 2009
    Posts
    468
    Har so I was right ^^

    Thanks
    Follow Math Help Forum on Facebook and Google+

  13. #13
    Newbie
    Joined
    Jan 2010
    Posts
    9
    How can't you split into right angled triangles??

    First use cosine rule to work out the length of the remaining side = 17.94cm

    Then use sine rule and basic calculation (180-angle = other angle) to work out

    BCA = 25.39
    CAB = 48.61

    Then use use trig functions (sine and cosine) to work out length and height of triangles

    And calculate the triangle with 1/2 base times height.

    A = 53.8cm2
    Follow Math Help Forum on Facebook and Google+

  14. #14
    Master Of Puppets
    pickslides's Avatar
    Joined
    Sep 2008
    From
    Melbourne
    Posts
    5,234
    Thanks
    27
    Quote Originally Posted by Mukilab View Post
    Har so I was right ^^

    Thanks
    Right on what exactly?

    Quote Originally Posted by Mukilab View Post
    This calculates to -40...... can't be the area.
    No you weren't

    Quote Originally Posted by e^(i*pi) View Post
    Using pickslide's method I get 58.8 as an answer
    I like this answer better.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Area of ellipsoid, working out the limits?
    Posted in the Calculus Forum
    Replies: 1
    Last Post: May 20th 2011, 04:56 AM
  2. working out area under the curve?!!
    Posted in the Calculus Forum
    Replies: 3
    Last Post: November 16th 2010, 03:18 PM
  3. something's not working
    Posted in the Calculus Forum
    Replies: 7
    Last Post: February 12th 2009, 04:36 PM
  4. Replies: 16
    Last Post: May 23rd 2008, 08:29 AM
  5. Working Alone
    Posted in the Math Topics Forum
    Replies: 5
    Last Post: January 11th 2007, 10:35 PM

Search Tags


/mathhelpforum @mathhelpforum