How do...

This is a discussion on How do... within the C++ Programming forums, part of the General Programming Boards category; How do you put in code on C++ [(cos^-1) which is found on calculators as shift cos]... what I am ...

  1. #1
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    How do...

    How do you put in code on C++ [(cos^-1) which is found on calculators as shift cos]...

    what I am trying to do is solve for theta...

    cos (theta) = Fy/Fx

    how would i put that in code?

  2. #2
    and the hat of wrongness Salem's Avatar
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    use the acos() function
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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    Do you have an IDE, like Borland CBuilder, MS Visual C++, or anything to that effect? If so, usually you can use the help function to search when you're just looking for a function.

    Searching cos would probably yield acos as an alternate result.

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    I use acos() but, it does not calculate properly

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    Are you assigning it to an integer variable? Make sure you're using a float.

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    Quote Originally Posted by MyDestiny
    I use acos() but, it does not calculate properly
    Post the code.

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    what do u mean float?
    i didn't assign it to anything

  8. #8
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    I keep getting...

    -1.#IND

    as my answer

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    What are you doing with it?

    You either need to use it in an expression or assign it to a variable.

    float accepts decimal values. Integers, as you know, cannot - int in C++ is the same as a real-life integer where no decimal values are allowed

  10. #10
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    Radians?

    All of the trig functions in <cmath> use radians, not degrees. Maybe that will help. (?)

  11. #11
    and the hat of wrongness Salem's Avatar
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    Example
    Code:
    #include<stdio.h>
    #include<math.h>
    
    int main(){
        double angle = 0.5; /* this is in radians */
        double c = cos( angle );
        double d = acos( c );
        printf( "%f %f %f\n", angle, c, d );
        return 0;
    }
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

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    All of the trig functions in <cmath> use radians, not degrees. Maybe that will help. (?)
    Exactly - I suspect this might be where the problem lies. Radians are ugly numbers, almost always involving a decimal point. Degrees are often the opposite - 270deg, 60 deg, 45 deg, etc.

    I think MyDestiny might be using integer containers but it's hard to say without seeing the code

  13. #13
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    I just wanted to let you all know that I figured out the answer... THANKS a bunch for your help!

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