ATN2

Returns the inverse tangent of the ratio of x and y.

ATN2(y,x) = ATAN(y/x)

This represents the angle in radians from the positive x-axis of a plane and the point (x, y) on it, with positive sign for the upper half-plane.

Syntax

ATN2( expr1, expr2 )

Arguments

Parameter Description
expr1 Numeric expression representing the y component.
expr2 Numeric expression representing the x component

Returns

Always returns a floating point result of the inverse tangent, in radians.

Notes

  • The result is given in radians, in the range (-π, π].
  • If the input value is NULL, the result is NULL.

Examples

Inverse tangent of (1, 0) (= π/2)

numbers=> SELECT ATN2(1,0);
atn2
----
1.5707963267948966

Inverse tangent of x=0.5, y=SQRT(3)/2 (= π/3, or 60°)

Use SQRT to simplify input and DEGREES to convert the result from radians.

numbers=> SELECT ATN2(0.5*SQRT(3), 0.5), DEGREES(ATN2(0.5*SQRT(3), 0.5));
atn2   | degrees
-------+--------
1.0472 |      60