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Math Help - arc tan, sin and cos

  1. #1
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    arc tan, sin and cos

    ok
    well my first questions dealing with inclination, i get how to do it though im having trouble calculating arctan.
    so the question goes as follow

    Find the inclination of the line 2x+3y=6.

    ***Solution****
    tan(@)=-2/3
    @=pie+arctan(-2/3)

    though i cant calculate arctan of -2/3 so can someone explain me how to calculate arctan. thank you and if you can give me an inside for arc sin and cos that would be great thanks.
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by ladventchildp View Post
    ok
    well my first questions dealing with inclination, i get how to do it though im having trouble calculating arctan.
    so the question goes as follow

    Find the inclination of the line 2x+3y=6.

    ***Solution****
    tan(@)=-2/3
    @=pie+arctan(-2/3)

    though i cant calculate arctan of -2/3 so can someone explain me how to calculate arctan. thank you and if you can give me an inside for arc sin and cos that would be great thanks.
    so arctan is just the inverse of tangent. we use it to solve for an angle. so in general:

    if sinx = y then x = arcsiny
    if cosx = y then x = arccosy
    if tanx = y then x = arctany
    and so on

    then you usually have to add k*pi, or 2k*pi depending on what interval you want to solve for and the particular problem. these functions are periodic, so they repeat the same values over and over, that's what the multiples of pi take care of

    do you understand how they ended up with tan@ = -2/3?
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  3. #3
    Forum Admin topsquark's Avatar
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    Quote Originally Posted by ladventchildp View Post
    ok
    well my first questions dealing with inclination, i get how to do it though im having trouble calculating arctan.
    so the question goes as follow

    Find the inclination of the line 2x+3y=6.

    ***Solution****
    tan(@)=-2/3
    @=pie+arctan(-2/3)

    though i cant calculate arctan of -2/3 so can someone explain me how to calculate arctan. thank you and if you can give me an inside for arc sin and cos that would be great thanks.
    If your question is how to calculate arctan(-2/3) you need to do it on a calculator. There is no "nice" angle theta such that tan(theta) = -2/3.

    -Dan
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  4. #4
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    yeah i understand how they got tan(-2/3) but i have a bit of difficulty finding the arctan of it, but ill impliment what you stated and see what happens thanks. and how would i calculate it using the calculator
    Last edited by ladventchildp; April 25th 2007 at 10:03 PM.
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  5. #5
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by ladventchildp View Post
    yeah i understand how they got tan(-2/3) but i have a bit of difficulty finding the arctan of it, but ill impliment what you stated and see what happens thanks. and how would i calculate it using the calculator
    usually, the buttons that do the trig function do the inverse trig functions as second functions

    so on your calculator, press 2ndF and then the button for tan and that will give you arctan or tan inverse, then enter the number you want
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  6. #6
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    Re:

    Quote Originally Posted by ladventchildp View Post
    yeah i understand how they got tan(-2/3) but i have a bit of difficulty finding the arctan of it, but ill implement what you stated and see what happens thanks. and how would i calculate it using the calculator
    RE:

    You need a graphing Calculator. I am an using the TI-89 Titanium Edition by Texas Instruments it will do just fine...

    One things for sure you WANT to change your mode from Radians to degrees...

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  7. #7
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    thanks alot i too have an 89 i just wasnt sure thanks man
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