Results 1 to 11 of 11

Math Help - Help finding x

  1. #1
    Junior Member
    Joined
    Mar 2008
    From
    Gibraltar
    Posts
    29

    Help finding x

    Hi can anybody show me how to find x?

    -180= -90 - tan^-1 (x/16) - tan^-1 (x/200)
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor Mathstud28's Avatar
    Joined
    Mar 2008
    From
    Pennsylvania
    Posts
    3,641

    There are multiple ways to do this

    Quote Originally Posted by al2308 View Post
    Hi can anybody show me how to find x?

    -180= -90 - tan^-1 (x/16) - tan^-1 (x/200)
    There is no alebraic way I am away of but you could do this... Say f(x)=90-arctan\bigg(\frac{x}{16}\bigg)-arctan\bigg(\frac{x}{200}\bigg) then we want f(x)=0...I would graph...or use the intermediate value theorem...or just use a graphing calculator
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Moo
    Moo is offline
    A Cute Angle Moo's Avatar
    Joined
    Mar 2008
    From
    P(I'm here)=1/3, P(I'm there)=t+1/3
    Posts
    5,618
    Thanks
    6
    Hello,

    This is straaaaaaaaaaaaaange

    90=arctan(x/16)+arctan(x/200)

    If we compose with tan, we have :

    tan(90)=tan(arctan(x/16)+arctan(x/200))

    But tan(90)= infinity :'(

    We can find somewhere the general formula for tan(a+b). I haven't looked further, maybe there is a solution though.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor Mathstud28's Avatar
    Joined
    Mar 2008
    From
    Pennsylvania
    Posts
    3,641
    Quote Originally Posted by Moo View Post
    Hello,

    This is straaaaaaaaaaaaaange

    90=arctan(x/16)+arctan(x/200)

    If we compose with tan, we have :

    tan(90)=tan(arctan(x/16)+arctan(x/200))

    But tan(90)= infinity :'(

    We can find somewhere the general formula for tan(a+b). I haven't looked further, maybe there is a solution though.
    He is right I am so used to putting cookie cutter responses to find the x...since tan\bigg(\frac{\pi}{2}\bigg)=\infty and the image of arctan(x) is \bigg(\frac{-\pi}{2},\frac{\pi}{2}\bigg)...therefore there is no solutions..that is unless this is in radians and not degrees? wait once again...I didnt look at this...I didnt read it right...sory
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    Quote Originally Posted by al2308 View Post
    Hi can anybody show me how to find x?

    -180= -90 - tan^-1 (x/16) - tan^-1 (x/200)
    You can solve this numerically (assuming that 180 and 90 are in degrees) to get x ~= 56.57

    RonL
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    Quote Originally Posted by Moo View Post
    Hello,

    This is straaaaaaaaaaaaaange

    90=arctan(x/16)+arctan(x/200)

    If we compose with tan, we have :

    tan(90)=tan(arctan(x/16)+arctan(x/200))

    But tan(90)= infinity :'(

    We can find somewhere the general formula for tan(a+b). I haven't looked further, maybe there is a solution though.
    Not significant because (slipping into radians) for instance:

    \pi/2=\arctan(\tan(\pi/4))+\arctan(\tan(\pi/4))

    and yet:

    \tan(\pi/2)=\tan(\arctan(\tan(\pi/4))+\arctan(\tan(\pi/4)))=\infty

    RonL
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Moo
    Moo is offline
    A Cute Angle Moo's Avatar
    Joined
    Mar 2008
    From
    P(I'm here)=1/3, P(I'm there)=t+1/3
    Posts
    5,618
    Thanks
    6
    Hm so there can be an analytic solution, or i really misunderstood your message

    Edit : ok, got it
    Follow Math Help Forum on Facebook and Google+

  8. #8
    Moo
    Moo is offline
    A Cute Angle Moo's Avatar
    Joined
    Mar 2008
    From
    P(I'm here)=1/3, P(I'm there)=t+1/3
    Posts
    5,618
    Thanks
    6
    Need verification (can't sleep until i find a correct method ), pleaaase, what d'you think of that ?


    (little mistake, it's 40 sqrt(2))

    (hey, it's the same as galactus's answer !)
    Attached Thumbnails Attached Thumbnails Help finding x-tistouille.jpg  
    Follow Math Help Forum on Facebook and Google+

  9. #9
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    Quote Originally Posted by Moo View Post
    Hm so there can be an analytic solution, or i really misunderstood your message

    Edit : ok, got it

    Well there could be a closed form solution in terms of elementary functions, but it is unlikely unless the problem has some special structure, but I can't see any here.

    (someone will be along in a minute to prove me wrong in this case - it always happens).

    RonL
    Follow Math Help Forum on Facebook and Google+

  10. #10
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    Quote Originally Posted by Moo View Post
    Need verification (can't sleep until i find a correct method ), pleaaase, what d'you think of that ?


    (little mistake, it's 40 sqrt(2))

    (hey, it's the same as galactus's answer !)
    Hey, you changed the answer before I could correct it.

    RonL
    Follow Math Help Forum on Facebook and Google+

  11. #11
    Moo
    Moo is offline
    A Cute Angle Moo's Avatar
    Joined
    Mar 2008
    From
    P(I'm here)=1/3, P(I'm there)=t+1/3
    Posts
    5,618
    Thanks
    6


    So is it ok this way ?

    PS : if you can reduce the size of the image, it would be wonderful as i have no idea how to do ^^'
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 10
    Last Post: December 8th 2011, 11:27 AM
  2. Replies: 1
    Last Post: July 3rd 2010, 11:40 PM
  3. Finding a limit. Finding Maclaurin series.
    Posted in the Calculus Forum
    Replies: 2
    Last Post: May 18th 2010, 11:04 PM
  4. Finding the radius, solving, and finding theta?
    Posted in the Trigonometry Forum
    Replies: 2
    Last Post: June 13th 2009, 03:37 PM
  5. Replies: 1
    Last Post: April 9th 2009, 10:02 AM

Search Tags


/mathhelpforum @mathhelpforum