coddding coddding - 11 days ago 5
C++ Question

C++ Creating Atan2 from Atan

How would i go about taking my

atan
function and make it into
atan2
?
For example

float myAtan2(double a, double b)
{
float atan2val = //calculate atan2 using atan
return atan2val;
}


Sorry I'm not the best at trigonometry!

Answer

Something like this:

float myAtan2(double a, double b)
{

    float atan2val;
    if (b > 0) {
        atan2val = atan(a/b);
    }
    else if ((b < 0) && (a >= 0) {
        atan2val = atan(a/b) + pi;
    }
    else if ((b < 0) && (a < 0) {
        atan2val = atan(a/b) - pi;
    }
    else if ((b = 0) && (a > 0)) {
        atan2val = pi / 2;
    }
    else if ((b = 0) && (a < 0)) {
        atan2val = 0 - (p / 2 );
    }
    else if ((b = 0) && (a = 0)) {
        atan2val = 1000;               //represents undefined
    }
    return atan2val;
}

You can probably code it prettier, but that's the logic, which I got from here: https://en.wikipedia.org/wiki/Atan2#Definition_and_computation.

I'm returning 1000 (an impossible value for an arctan) to represent "undefined". You could do it some other way maybe by using NaN or something.

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