Math 6B, Fall 2023 Practice final exam
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Practice final exam
Math 6B, Fall 2023
Problem 1. [10 points] Let F : R2 → R2 be the vector field defined by
F(x,y) = (−y, ey3 + x)
and let C+ be the part of the circle x2 + y2 = 1 with y ≥ 0 oriented from (1, 0) to (−1, 0).
Compute the line integral
lC+ F · dr.
Problem 2. [10 points] Let f : R3 → R be the function defined by
f(x,y, z) = 1 +“1 + x2 + y2
and let S be the part of the paraboloid 2z = x2 + y2 with z ≤ 8. Compute the surface integral
llS f dS.
Problem 3. [10 points] Let F : R3 一 R3 be the vector field defined by
F(x,y, z) =( —ezy,ezx,(log(x2 + 3y2 + 1))3 — cos(x2 — 3y + 1))
and let S+ be the part of the hyperboloid x2 + y2 — z2 = 1 with — 2 三 z 三 2 oriented by the unit normal vectors pointing away from the z-axis. Compute the surface integral
llS+ (Δ X F) · dS.
Problem 4. [10 points] Let F : R3 → R3 be the vector field defined by
F(x,y, z) = (x − 2, y + 1, z)
and let S+ be the sphere x2 + y2 + z2 = 16 with outwards orientation. Compute the surface
integral
llS+ F · dS.
Problem 5. [10 points] Find the Fourier sine series and the Fourier cosine series of the function f : [0, 1] ⊂ R → R defined by f(x) = x2 .
Problem 6. [10 points] Solve the following initial boundary value problem:
ut = uxx , 0 < x < 1, t > 0;
〈 u(0, t) = −1, u(1, t) = 2, t > 0;
( u(x,0) = 3x − 1 + sin(πx) − 3sin(5πx), 0 < x < 1.
Problem 7. [10 points] Solve the following initial boundary value problem:
ut = uxx − 7u, 0 < x < 3, t > 0;
〈 u(0, t) = 0, u(3, t) = e3√7 − e−3√7 , t > 0;
u(x,0) = e√7x − e−√7x + 2sin , 0 < x < 3.
Problem 8. [10 points] Solve the following initial boundary value problem:
utt = uxx − x2 sin(t) − 2sin(t), 0 < x < 5, t ∈ R;
u(u)) s3(x)x(5)t01x(in)); t ∈ R;
ut (x,0) = x2 + 1 + cos ( 5(πx)) , 0 < x < 5.
Hint: First show that the function φ(x,t) = x2 sin(t) is a solution of the PDE
utt = uxx − x2 sin(t) − 2sin(t).
2023-12-15