Method: Math.atan2

Defined in:
math.c

.atan2(y, x) ⇒ Float

Computes the arc tangent given y and x. Returns a Float in the range -PI..PI.

Domain: (-INFINITY, INFINITY)

Codomain: [-PI, PI]

Math.atan2(-0.0, -1.0) #=> -3.141592653589793
Math.atan2(-1.0, -1.0) #=> -2.356194490192345
Math.atan2(-1.0, 0.0)  #=> -1.5707963267948966
Math.atan2(-1.0, 1.0)  #=> -0.7853981633974483
Math.atan2(-0.0, 1.0)  #=> -0.0
Math.atan2(0.0, 1.0)   #=> 0.0
Math.atan2(1.0, 1.0)   #=> 0.7853981633974483
Math.atan2(1.0, 0.0)   #=> 1.5707963267948966
Math.atan2(1.0, -1.0)  #=> 2.356194490192345
Math.atan2(0.0, -1.0)  #=> 3.141592653589793
Math.atan2(INFINITY, INFINITY)   #=> 0.7853981633974483
Math.atan2(INFINITY, -INFINITY)  #=> 2.356194490192345
Math.atan2(-INFINITY, INFINITY)  #=> -0.7853981633974483
Math.atan2(-INFINITY, -INFINITY) #=> -2.356194490192345

Returns:



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# File 'math.c', line 64

static VALUE
math_atan2(VALUE obj, VALUE y, VALUE x)
{
#ifndef M_PI
# define M_PI 3.14159265358979323846
#endif
    double dx, dy;
    Need_Float2(y, x);
    dx = RFLOAT_VALUE(x);
    dy = RFLOAT_VALUE(y);
    if (dx == 0.0 && dy == 0.0) {
	if (!signbit(dx))
	    return DBL2NUM(dy);
        if (!signbit(dy))
	    return DBL2NUM(M_PI);
	return DBL2NUM(-M_PI);
    }
#ifndef ATAN2_INF_C99
    if (isinf(dx) && isinf(dy)) {
	/* optimization for FLONUM */
	if (dx < 0.0) {
	    const double dz = (3.0 * M_PI / 4.0);
	    return (dy < 0.0) ? DBL2NUM(-dz) : DBL2NUM(dz);
	}
	else {
	    const double dz = (M_PI / 4.0);
	    return (dy < 0.0) ? DBL2NUM(-dz) : DBL2NUM(dz);
	}
    }
#endif
    return DBL2NUM(atan2(dy, dx));
}