import type { ReadonlyVec } from "./api.js";
/**
 * Returns orientation angle (in radians) of vector `a` in XY plane.
 *
 * @param a -
 */
export declare const headingXY: (a: ReadonlyVec) => number;
/**
 * Returns orientation angle (in radians) of vector `a` in XZ plane.
 *
 * @param a -
 */
export declare const headingXZ: (a: ReadonlyVec) => number;
/**
 * Returns orientation angle (in radians) of vector `a` in ZY plane.
 *
 * @param a -
 */
export declare const headingYZ: (a: ReadonlyVec) => number;
/**
 * Same as {@link headingXY}
 */
export declare const heading: (a: ReadonlyVec) => number;
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