/**
 * safe math functions, avoids returning NaN
 * Warning: You should know what you are doing!
 */
/**
 * Returns the tangent of a number.
 * @param x A numeric expression that contains an angle measured in radians.
 * @returns always a number, no NaN
 */
export declare function tan(x: number): number;
/**
 * Returns the arcsine of a number.
 * @param x A numeric expression.
 * @returns always a number, no NaN
 */
export declare function asin(x: number): number;
/**
 * Returns the arc cosine (or inverse cosine) of a number.
 * @param x A numeric expression.
 * @returns always a number, no NaN
 */
export declare function acos(x: number): number;
/**
 * Returns the square root of a number.
 * @param x A numeric expression.
 * @returns always a number, no NaN
 */
export declare function sqrt(x: number): number;
