import type { ArrayVector2D } from "./types.js";
/**
 * Gets the angle between a 2D vector and the positive x-axis in radians.
 * @param {ArrayVector2D} xy - Vector as `[x, y]`
 * @returns {number} Angle in radians, always in the range [0, 2π)
 */
export declare const angleX2D: (xy: ArrayVector2D) => number;