calculus III

9. Find the principal unit normal vector for the curve : r(t) = (3 cos(t), 3 sin(t), 4t) 10. Find the normal and the tangential components of the acceleration for the curve given by 7 (t ) = tit V6 2 11. (Extra Credit) Suppose that a * 0 i.) If a . b = a . Z, does it follow that b = c, give an example . ii.) If a x b = a x c, does it follow that b = c, give an example . iii.) If a . b = a . d and axb = a x c, does it follow that b = a iv.) Prove that a . (bx c) = b . (cx a) = c. (axb)