2. Consider the function f : R2 → R defined below. r3уг_ if (x,y) (0,0) f(x,y) = if (x, y) (0, 0) (a) Prove that f is continuous at (0,0) (b) Calculate the partial derivatives (0,0) and (0,0) directly from the definition of partial derivatives. (c) Prove that f is not differentiable at (0,0).
*Let f : R2 -R be given by z, y)(0,0 r, y)- 2y and f(0,0) = 0. (a) Decide if both partial derivatives of f exist at (0, 0) (b) Decide if f has directional derivatives along all v R2 and if so compute these. (c) Decide if f is Fréchet differentiable at (0, 0)? (d) What can you infer about the continuity of the partial derivatives at (0, 0)? て
Let U be an open subset of R". Let f:UCR"-R be differentiable at a E U. In this exercise you will prove that if ▽f(a) 0, then at the point a, the function f increases fastest in the direction of V f(a), and the maximum rate of increase is Vf(a)l (a) Prove that for each unit vector u e R" (b) Prove that if ▽/(a)メ0, and u = ▽f(a)/IV/(a) 11, then Let U be an open subset of R". Let...
2. Let f: R R be a continuous function. Suppose that f is differentiable on R\{0} and that there exists an L e R such that lim,of,(z) = L. Prove that f is differentiable at 1-0 with f,(0) = L. (Hint: Use the definition of derivative and then use mean value theorem) 2. Let f: R R be a continuous function. Suppose that f is differentiable on R\{0} and that there exists an L e R such that lim,of,(z) =...
2. Let f(x, y) = xy (2] (a) Findäf af and Vf. 5 (b) Find a unit vector u for which Duf(v2, V2) = 0. 2. Let f(x, y) = xy (2] (a) Findäf af and Vf. 5 (b) Find a unit vector u for which Duf(v2, V2) = 0.
3. (a) Let f be an infinitely differentiable function on R and define F(x) = [-vf(u) dy. Find and prove a formula for F(n), the nth derivative of F. (b) Show that if f is a polynomial then there exists a constant C such that F(n)(x) = Cea for sufficiently large n. Find the least n for which it is true.
Problem #7: Let R = r \ {(0,0,0)) and F is a vector field defined on R satisfying curl(F) = 0. Which of the following statements are correct? [2 marks] (1) All vector fields on R are conservative. (ii) All vector fields on Rare not conservative. (iii) There exists a differentiable function / such that F - Vf. (iv) The line integral of Falong any path which goes from (1,1,1) to (-2,3,-5) and does not pass through the origin, yields...
(6 points) Are the following statements true or false? 1. fi (a, b) is parallel to u 2.If iü is a unit vector, then fila, b) is a vector ? 3. Suppose f(a, b) and f(a, b) both exist. Then there is always a direction in which the rate of change of f at (a, b) is zero ?4.I f(x, y) has f. (a, b) 0 and f,(a, b) 0at the point (a, b), then f is constant everywhere |...
if (r.y) (0,0), 0,f (, y) (0, 0) 2. Consider f : IR2 -R defined by f(r,y)-+ (a) Show by explicit computation that the directional derivative exists at (x, y)- (0,0) for all oi rections u є R2 with 1 11-1, but that its value %(0.0) (Vf(0,0).u), fr at least one sucli u. (b) Show that the partial derivatives of f are not continuous at (0,0) if (r.y) (0,0), 0,f (, y) (0, 0) 2. Consider f : IR2 -R...
1(a) Let f : R2 → R b constant M > 0 such that livf(x,y)|| (0.0)-0. Assume that there exists a e continuously differentiable, with Mv/r2 + уг, for all (z. y) E R2 If(x,y)| 〈 M(x2 + y2)· for all (a·y) E R2 Prove that: 1(a) Let f : R2 → R b constant M > 0 such that livf(x,y)|| (0.0)-0. Assume that there exists a e continuously differentiable, with Mv/r2 + уг, for all (z. y) E R2...