Use this to explain why if you have a curve P[t] in three dimensions, then binormal[t] = unittan[t] mainunitnormal[t] is a unit vector perpendicular to the curve at P[t] and perpendicular to mainunitnormal[t] at P[t]. Use this to explain why if you have a curve P[t] in three dimensions, then binormal[t] = unittan[t] mainunitnormal[t] is a unit vector perpendicular to the curve at P[t] and perpendicular to mainunitnormal[t] at P[t]