For f(x, y) = 3 sin(x + y), find the mixed second partial derivative ∂²f/∂x∂y at (1, 2).
Multivariable calculus worksheet with answers
1.Easy
f(x, y) = 3 sin(x + y)P = (1, 2)
fxy(1, 2) =
2.Easy
For f(x, y) = −4xy² + 3x³ − 4y² + 2xy, find the partial derivative ∂f/∂y at the point (1, −3).
f(x, y) = −4xy² + 3x³ − 4y² + 2xyP = (1, −3)
fy(1, −3) =
3.Medium
The tangent plane to z = 4x²y² + 3x³ at the point where (x, y) = (1, 3) can be written as z = px + qy + c. Find c.
f(x, y) = 4x²y² + 3x³(a, b) = (1, 3)
c =
4.Medium
For f(x, y) = −2xey, find the directional derivative Duf at (1, −1) in the direction of v = (2, 2).
f(x, y) = −2xeyP = (1, −1)v = (2, 2)
Duf =
5.Hard
Use polar coordinates to evaluate I = ∬R e−(x² + y²) dA, where R is the quarter of the disc x² + y² ≤ 2.25 in the first quadrant.
f = e−(x² + y²)0 ≤ r ≤ 1.50 ≤ θ ≤ π/2
I =
6.Hard
Use polar coordinates to evaluate I = ∬R √(x² + y²) dA, where R is the quarter of the disc x² + y² ≤ 4 in the first quadrant.
f = √(x² + y²)0 ≤ r ≤ 20 ≤ θ ≤ π/2
I =
Answer key
- 1. fxy(1, 2) = −0.4234
- 2. fy(1, −3) = 50
- 3. c = −114
- 4. Duf = −1.041
- 5. I = 0.7026
- 6. I = 4.189
Full step-by-step solutions: practise this topic on examproblems.com.