Vector Calculus Exam 2: October 18th, Exams of Calculus

Vector calculus exam 2 held on october 18th. The exam consists of 7 problems with a total of 144 points. It includes questions related to gradient, directional derivatives, temperature estimation, chain rule, and critical points.

Typology: Exams

2012/2013

Uploaded on 02/18/2013

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Name:______________________________
Vector Calculus Exam 2 October 18th
There are 7 problems and 144 points total. The point value of each question is indicated. Read each
question carefully!
1. (24 points.) Let 23 3),( xyxyxf += and yxyyxg 23 3),( += Compute the following
a.
()
=+
),(),( yxgyxf
x
b.
()
=
),(),( yxgyxf
y
c. (2 ( , ))fxy∇=
2. Use the figure below to answer the following questions
a) (3 points) What is the sign of the derivative at point A in the direction of the vector shown at A?
b) (3 points) What is the sign of the derivative at point B in the direction of the vector shown at B?
c) (6 points) Draw a vector in the direction of the gradient at point A
d) (6 points) Draw a vector in the direction of the gradient at point B.
pf3
pf4
pf5

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Name:______________________________

Vector Calculus Exam 2 October 18th

There are 7 problems and 144 points total. The point value of each question is indicated. Read each question carefully!

1. (24 points.) Let f ( x , y )= x^3 + 3 xy^2 and g ( x , y )= y^3 + 3 x^2 y Compute the following

a. ( + ) =

∂ (^) f ( x , y ) g ( x , y ) x

b. (^ − )^ =

∂ (^) f ( x , y ) g ( x , y ) y

c. ∇ (2 f ( , x y ))=

2. Use the figure below to answer the following questions

a) (3 points) What is the sign of the derivative at point A in the direction of the vector shown at A?

b) (3 points) What is the sign of the derivative at point B in the direction of the vector shown at B?

c) (6 points) Draw a vector in the direction of the gradient at point A

d) (6 points) Draw a vector in the direction of the gradient at point B.

3. (18 points.). Find the derivative of f ( , x y ) = 9 cos( ) x + 16 y at the point ( , x y ) = ( 0,1)in the

direction (3,5)

4. (12 points.) A large metal plate is being chilled unevenly. The loss of heat causes each point ( , x y )

to have temperature T x y ( , ) measured in o^ F. We know that T (0,1) = 5 , Tx (0,1) = 0 , and Ty (0,1) = 85.

Estimate the temperature at the point (0.02, 0.95)

b) (16 points) Use the chain rule to compute z v

c) (4 points) Compute ∇ z u v ( , )

7. Let

2 2

f ( , x y ) = e x^ + y

a) (8 points) Find the critical points of f(x,y)

b) (16 points) Compute f^ xy ( , x y^^ ) and f^ yx ( , x y^^ ) and verify that f^ xy ( , x y^ )^^ =^ f^ yx ( , x y^ ),