getTangentAt( u, optionalTarget ) {

		const t = this.getUtoTmapping( u );
		return this.getTangent( t, optionalTarget );

	}
Same as {@link Curve#getTangent} but with equidistant samples.

@param {number} u - The interpolation factor.
@param {(Vector2|Vector3)} [optionalTarget] - The optional target vector the result is written to.
@return {(Vector2|Vector3)} The tangent vector.
@see {@link Curve#getPointAt}