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The final exam for the math206a multivariable calculus course taught by prof. P. Wong, held on december 12, 2007. The exam covers various topics in multivariable calculus, including critical points, change of variables, directional derivatives, green's theorem, line integrals, work, divergence, gauss' theorem, and stokes' theorem.
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FINAL EXAM - DECEMBER 12, 2007
NAME:
Instruction: Read each question carefully. Explain ALL your work and give reasons to support your answers. Advice: DON’T spend too much time on a single problem.
Problems Maximum Score Your Score
1
2 FINAL EXAM - DECEMBER 12, 2007
f (x, y) = 3x^3 + y^2 − 9 x + 4y and g(t) = (t
2 6 , e
t/ (^3) , 1 − t).
(8 pts) (i) Classify all critical points of f (local max/min, saddle points, etc.).
(7 pts.) (ii) Find the Jacobian matrix J(g ◦ f )(0, 1) of g ◦ f at (0, 1).
4 FINAL EXAM - DECEMBER 12, 2007
(5 pts) (i) Find the directional derivative DuF (1, 1 , 1) of F at the point (1, 1 , 1) in the direction of u = 2i − j + 2k.
(5 pts) (ii) Find a direction (give a unit vector) in which F decreases most rapidly at the point (1, 1 , 1).
(5 pts) (iii) Find an equation of the plane tangent to the level surface F (x, y, z) = 2 at the point (1, 1 , 1).
MATH206A MULTIVARIABLE CALCULUS - PROF. P. WONG 5
2 xy dx + (x + 1)^2 dy.
(12 pts) (ii) Let F (x, y) = (−e−x^ ln y, e− yx ). Determine whether the vector field F is path independent. If so, find a function f so that ∇f = F.
MATH206A MULTIVARIABLE CALCULUS - PROF. P. WONG 7
(10 pts) (ii) Use Gauss’ (or Divergence) theorem to evaluate the flux of the vector field F (^) ∫∫
∂S
© F · n dσ
where ∂S is the surface of the rectangular box S determined by
0 ≤ x ≤ 1 , 0 ≤ y ≤ 2 , 0 ≤ z ≤ 3.
8 FINAL EXAM - DECEMBER 12, 2007
M
(5 pts.)(i) Find curl F.
(5 pts.)(ii) Write a parametrization for the surface M. Be sure to indicate the domains for the parameters.
(10 pts.)(iii) Use Stokes’ theorem to evaluate the path integral ∮ ∂M
F · dx [Hint: Use parts (i) and (ii).].