Results 1 to 4 of 4

Math Help - Some trig problems, fast help would be great!

  1. #1
    Junior Member
    Joined
    Sep 2008
    Posts
    41

    Some trig problems, fast help would be great!

    Hi everyone. Can someone please explain these questions?


    1) Find the exact value of cos 105 degrees

    how would i go about doing that? it's not just a simple calculator problem, but rather one probably involving 30-60-90 or 45-45-90 triangles. the answer has radicals in it.

    2) A surveyor determines that the angle of elevation of a mountain peak is 35 degrees. Moving 1000 feet further away from the mountain, the surveyor determines the angle of elevation to be 30 degrees. Find the mountain's height.

    Thanks!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by gobbajeezalus View Post
    Hi everyone. Can someone please explain these questions?


    1) Find the exact value of cos 105 degrees

    how would i go about doing that? it's not just a simple calculator problem, but rather one probably involving 30-60-90 or 45-45-90 triangles. the answer has radicals in it.
    Hint: cos(105) = cos(60 + 45). now use the addition formula for cosine and continue

    2) A surveyor determines that the angle of elevation of a mountain peak is 35 degrees. Moving 1000 feet further away from the mountain, the surveyor determines the angle of elevation to be 30 degrees. Find the mountain's height.

    Thanks!
    did you draw a diagram? if not, do so. you will realize the following:

    Let the height of the mountain be y
    Let the first position of the surveyor be x feet from the mountain. then

    \tan 35^o = \frac yx

    \tan 30^o = \frac y{x + 1000}

    you have two simultaneous equations with two unknowns, you are required to solve for one of them, namely y
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Sep 2008
    Posts
    41
    PERFECT! #1 works like a charm.

    as far as #2 goes, i'm not really sure how to proceed. i got it up to the diagram part, and i completely understand the equations provided, but how do i set them equal to each other?

    thanks
    Follow Math Help Forum on Facebook and Google+

  4. #4
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by gobbajeezalus View Post
    PERFECT! #1 works like a charm.

    as far as #2 goes, i'm not really sure how to proceed. i got it up to the diagram part, and i completely understand the equations provided, but how do i set them equal to each other?

    thanks
    one way: solve for x inthe first equation and plug it into the second. you will then have an equation where only y is unknown, you can solve for it
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Combinatorics Problems - great fun
    Posted in the Statistics Forum
    Replies: 2
    Last Post: November 24th 2008, 05:14 PM
  2. need help fast for trig
    Posted in the Trigonometry Forum
    Replies: 4
    Last Post: July 9th 2008, 01:01 PM
  3. Great Trig Lesson with Humour!
    Posted in the Trigonometry Forum
    Replies: 6
    Last Post: March 13th 2008, 06:35 AM
  4. lots of math problems, and fast????
    Posted in the Math Topics Forum
    Replies: 7
    Last Post: August 13th 2007, 06:42 AM
  5. Please Need Help Fast World Problems
    Posted in the Math Topics Forum
    Replies: 8
    Last Post: December 13th 2006, 11:55 PM

Search Tags


/mathhelpforum @mathhelpforum