Frenet-Serret formulas (프레네-세레 공식)
The tangent, normal, and binormal unit vectors, often called T , N , and B , or collectively the Frenet–Serret frame or TNB frame , together form an orthonormal basis spanning ℝ 3 and are defined as follows: T is the unit vector tangent to the curve, pointing in the direction of motion. N is the normal unit vector, the derivative of T with respect to the arclength parameter of the curve, divided by its length. B is the binormal unit vector, the cross product of T and N . The Frenet–Serret formulas are: where d / ds is the derivative with respect to arclength, κ is the curvature , and τ is the torsion of the curve. The two scalars κ and τ effectively define the curvature and torsion of a space curve. The associated collection, T ,...