Member Avatar for reincom 
public class PolarCoordinates {

    public static void main(String[] args){

        int r=10;
        double x=0,y=0,theta=30;
     x=r*Math.cos(theta);
    y=r*Math.sin(theta);

        System.out.println("The value of x is :" +x);
        System.out.println("The value of y is :" +y);



}
}

help please?
it gives me wrong answer.
10cos(30) should equal to 8.7, but it gives me 11.7 ans.
10sin(30) should equal to 5, and it gives me 2.63 ans.
whats wrong with my code?

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Dani AI

Generated

As noted, Java’s trig functions take radians, which is why ’s degree value produced unexpected results. correctly pointed toward converting the angle — the clearest, least error‑prone way in Java is to use Math.toRadians(...) before calling Math.cos/Math.sin.

int r = 10;
double degrees = 30.0;
double rad = Math.toRadians(degrees);
double x = r * Math.cos(rad);
double y = r * Math.sin(rad);
System.out.printf("x = %.3f, y = %.3f%n", x, y);

Quick practical tips not covered above: when using these coordinates for drawing in a GUI remember screen Y usually grows downward — invert the sine term or subtract from the canvas origin if you need a traditional Cartesian orientation. Also watch out for integer math when converting manually (e.g., 1/180 as integers yields 0); prefer Math.toRadians or do the conversion with doubles. Verify behavior with known angles (0°, 90°, 180°, 270°) to make sure your orientation and sign are what you expect.

Finally, keep angles as doubles, format output for readability, and, if you compute many points, compute the radian once and reuse it rather than converting inside loops.

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All 7 Replies

Member Avatar for JamesCherrill

sin. cos etc use angles in radians, your data (30) looks like degrees.

Member Avatar for ddanbe

30° equals pi/6 rad

Member Avatar for reincom

oh yes, its a degrees.
what's wrong with my formula?

Member Avatar for ddanbe

To convert yout theta value from degrees to radians use: theta = (theta * 3.141592)/360;

Member Avatar for JamesCherrill

what's wrong with my formula?

sin. cos etc use angles in radians (Google it), you have supplied an angle in degrees

Pi radians is 180 degrees, so ddanbe' formula should be theta = theta * Math.PI / 180;
(sorry ddanbe)

Edited by JamesCherrill
Member Avatar for ddanbe

Oops!!! Thanks for correcting me JamesCherrill, 2*pi rad = 360° and not pi rad = 360° of course!

Member Avatar for reincom

ohh, ok! thanks! i got it now :)

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