数学arctan在android项目中不起作用

Question

In the following code,

float i = Float.parseFloat(a);
float j = Float.parseFloat(b);
double div = (double)j/i;  
float theta = (float) Math.atan(Math.toRadians(div));

theta gets the wrong value. As far I can see, it always computes Math.tan (I tried this also and it gives me the same results). So even if I write Math.tan or Math.atan , I get the same results.

Can anyone help me?

Specific examples:

i,j----> theta I get:

3,4-----> 0.023 while the correct one is arctan(4/3)=53.13 not tan(4/3)=0.023
3,6-----> 0.052 while the correct one is arctan(9/3)=71.56 not tan(9/3)=0.052

Answer 1

Looks like you're converting oddly all over the place. Here's what I think you want:

public class Test {
    public static void main(String[] args) throws Exception {
        double div = (double)4/3;  
        float theta = (float) Math.toDegrees(Math.atan(div));
        System.out.println(theta); // 53.130104
    }
}

Assuming you want 4/3 as the gradient, that isn't an angle at all - so calling Math.toRadians on it is inappropriate. You want to call Math.atan on the gradient to get the value in radians, and then Math.toDegrees on the radians value to get degrees.