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Math Help - sin and cosin vs degrees and radians???

  1. #1
    Newbie
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    Nov 2011
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    sin and cosin vs degrees and radians???

    First off, math is not my strong suit. Just wanted to get that out of the way. Now here's my question. Here's a link with the equations... High Performance Math ... I'm curious on the 3rd step... up to that point I get...

    intake cam degrees = intake valve duration
    2


    142 (degrees) = 284
    2

    theta = 90 - intake cam degrees
    2


    19 ( Theta) = 90 - 71

    Now, here's where I'm stuck....

    x = 0.5cos(3.14/(180 / theta))
    y = 0.5sin(3.14/(180 / theta))


    I'm not certain on the cos/sin part of the equations. Reason I ask is cause when I use my calculator (WINDOWS CALCULATOR), depending on whether I have DEGREES or RADIANS selected, I get 2 different answers for sin/ cosin.

    With degrees I get a 0.99996192306417 cos and with radians I get 0.87758256189037.
    With degrees I get 0.0087265354983739 sin and with radians I get 0.4794255386042.


    Maybe someone can clarify... I'm trying to input the info in EXCEL but the program only calculates it out in radians... Do those equations already consider Radians and give answers in degrees or do I have to covert from radians to degrees. If so, how do I do that. Hope someone can help.



    Thanks.
    ROB
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  2. #2
    Grand Panjandrum
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    Re: sin and cosin vs degrees and radians???

    Quote Originally Posted by roboz View Post
    First off, math is not my strong suit. Just wanted to get that out of the way. Now here's my question. Here's a link with the equations... High Performance Math ... I'm curious on the 3rd step... up to that point I get...

    intake cam degrees = intake valve duration
    2


    142 (degrees) = 284
    2

    theta = 90 - intake cam degrees
    2


    19 ( Theta) = 90 - 71

    Now, here's where I'm stuck....

    x = 0.5cos(3.14/(180 / theta))
    y = 0.5sin(3.14/(180 / theta))


    I'm not certain on the cos/sin part of the equations. Reason I ask is cause when I use my calculator (WINDOWS CALCULATOR), depending on whether I have DEGREES or RADIANS selected, I get 2 different answers for sin/ cosin.

    With degrees I get a 0.99996192306417 cos and with radians I get 0.87758256189037.
    With degrees I get 0.0087265354983739 sin and with radians I get 0.4794255386042.


    Maybe someone can clarify... I'm trying to input the info in EXCEL but the program only calculates it out in radians... Do those equations already consider Radians and give answers in degrees or do I have to covert from radians to degrees. If so, how do I do that. Hope someone can help.



    Thanks.
    ROB
    3.14/(180 / theta)=theta*3.14/180

    is the approximate conversion of theta in degrees into radians, so set the calculator to radians (and make sure theta is in degrees to start with).

    CB
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  3. #3
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    Joined
    Nov 2011
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    Re: sin and cosin vs degrees and radians???

    Okay, so the equation converts degrees to radians. Gotcha. Now my other question. Further down the page, with these sets of equations, I assume there is a misprint in the following 2 formulas? Correct?

    yn4 = -a(-0.4) + b
    yn3 = -a(-0.3) + b
    yn2 = -a(-0.4) + b <----- Value should be -0.2 instead of -0.4?
    yn1 = -a(-0.1) + b
    y0 = -a(0.1) + b <--- Shouldn't the value in parentheses be 0 instead of 0.1 ?
    y1 = -a(0.1) + b
    y2 = -a(0.2) + b
    y3 = -a(0.3) + b
    y4 = -a(0.4) + b

    I assume its a misprint, but they also write the formula the same on this page... High Performance Math .... So I'd rather ask just to be certain.

    Thanks again for the help.
    Rob
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  4. #4
    Grand Panjandrum
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    4

    Re: sin and cosin vs degrees and radians???

    Quote Originally Posted by roboz View Post
    Okay, so the equation converts degrees to radians. Gotcha. Now my other question. Further down the page, with these sets of equations, I assume there is a misprint in the following 2 formulas? Correct?

    yn4 = -a(-0.4) + b
    yn3 = -a(-0.3) + b
    yn2 = -a(-0.4) + b <----- Value should be -0.2 instead of -0.4?
    yn1 = -a(-0.1) + b
    y0 = -a(0.1) + b <--- Shouldn't the value in parentheses be 0 instead of 0.1 ?
    y1 = -a(0.1) + b
    y2 = -a(0.2) + b
    y3 = -a(0.3) + b
    y4 = -a(0.4) + b

    I assume its a misprint, but they also write the formula the same on this page... High Performance Math .... So I'd rather ask just to be certain.

    Thanks again for the help.
    Rob
    Yes, they are misprints.

    CB
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