Results 1 to 15 of 15

Math Help - Tangent Help

  1. #1
    Member
    Joined
    May 2007
    Posts
    150

    Tangent Help

    How do you find the tangent of an angle without a calculator?

    Like a 30 degree angle, whats the diagram or proof for it?

    thanks
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Bar0n janvdl's Avatar
    Joined
    Apr 2007
    From
    Meh
    Posts
    1,630
    Thanks
    6
    Here you go...
    Attached Thumbnails Attached Thumbnails Tangent Help-driehoeke.jpg  
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member
    Joined
    May 2007
    Posts
    150
    thanks alot!

    what about 15 degree?
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Bar0n janvdl's Avatar
    Joined
    Apr 2007
    From
    Meh
    Posts
    1,630
    Thanks
    6
    15 degree is the value of 45 degree minus 30 degree

    But you need special identities to calculate for example: sin(45 - 30)
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Member
    Joined
    May 2007
    Posts
    150
    but isnt there a way using a 30 60 90, mabe bisecting the 30 and finding out the tangent of 15..with no calc at all
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Bar0n janvdl's Avatar
    Joined
    Apr 2007
    From
    Meh
    Posts
    1,630
    Thanks
    6
    Unfortunately no, not unless you have values for the sides.

    There isnt really a shortcut.
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Member
    Joined
    May 2007
    Posts
    150

    thats what i have so far
    Follow Math Help Forum on Facebook and Google+

  8. #8
    Bar0n janvdl's Avatar
    Joined
    Apr 2007
    From
    Meh
    Posts
    1,630
    Thanks
    6
    Cos 15 will give you the value of bd.

    Then Pythagoras will give you the value of ad.

    And you are given that (root3)/2 = ad/dc.

    So then you can calculate dc.
    Follow Math Help Forum on Facebook and Google+

  9. #9
    Member
    Joined
    May 2007
    Posts
    150
    ahhh great idea

    thanks
    Follow Math Help Forum on Facebook and Google+

  10. #10
    Member
    Joined
    May 2007
    Posts
    150
    hha
    now im simplifying

    tan(15) = root( (root3/cos15)^2 - (root3)^2 ) / root3

    but without solving the tans and cos and roots...(basically no calc at all)
    Follow Math Help Forum on Facebook and Google+

  11. #11
    Bar0n janvdl's Avatar
    Joined
    Apr 2007
    From
    Meh
    Posts
    1,630
    Thanks
    6
    It did take a lil good old trig to get there.
    Follow Math Help Forum on Facebook and Google+

  12. #12
    Member
    Joined
    May 2007
    Posts
    150
    can i even simplify that besides change the root3^2 to 3?
    Follow Math Help Forum on Facebook and Google+

  13. #13
    Bar0n janvdl's Avatar
    Joined
    Apr 2007
    From
    Meh
    Posts
    1,630
    Thanks
    6
    Tan 15 = ad/root3

    = (1/cos 15) - 1
    Follow Math Help Forum on Facebook and Google+

  14. #14
    Bar0n janvdl's Avatar
    Joined
    Apr 2007
    From
    Meh
    Posts
    1,630
    Thanks
    6
    I hope all this helped you.
    Follow Math Help Forum on Facebook and Google+

  15. #15
    Member
    Joined
    May 2007
    Posts
    150
    it did

    its all very appreciated!
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 1
    Last Post: September 27th 2011, 12:17 PM
  2. Replies: 6
    Last Post: January 12th 2011, 02:38 PM
  3. Replies: 6
    Last Post: April 7th 2010, 02:34 PM
  4. Tangent
    Posted in the Calculus Forum
    Replies: 3
    Last Post: March 8th 2010, 04:42 AM
  5. Replies: 3
    Last Post: February 20th 2009, 05:28 AM

Search Tags


/mathhelpforum @mathhelpforum