For f(x, y) = 2 ln(x² + 4y²), find the partial derivative ∂f/∂y at the point (2, 2).
Multivariable calculus worksheet with answers
1.Easy
f(x, y) = 2 ln(x² + 4y²)P = (2, 2)
fy(2, 2) =
2.Easy
For f(x, y) = 2 sin(3x + 3y), find the partial derivative ∂f/∂y at the point (−1, 0.5).
f(x, y) = 2 sin(3x + 3y)P = (−1, 0.5)
fy(−1, 0.5) =
3.Medium
For f(x, y) = −3x²y³ − 5x² + 3y³ − 4xy, find the directional derivative Duf at P(−1, −1) in the direction towards Q(−5, −1).
f(x, y) = −3x²y³ − 5x² + 3y³ − 4xyP = (−1, −1)Q = (−5, −1)
Duf =
4.Medium
For f(x, y) = 4x³y − 5x³ − 2xy, find the directional derivative Duf at (−2, −2) in the direction of v = (0, 4).
f(x, y) = 4x³y − 5x³ − 2xyP = (−2, −2)v = (0, 4)
Duf =
5.Hard
Use polar coordinates to evaluate I = ∬R √(x² + y²) dA, where R is the upper half of the disc x² + y² ≤ 1 (y ≥ 0).
f = √(x² + y²)0 ≤ r ≤ 10 ≤ θ ≤ π
I =
6.Hard
The integral I = ∫01.2 ∫y1.2 sin(x²) dx dy cannot be done in this order. Reverse the order of integration and evaluate it.
f = sin(x²)0 ≤ y ≤ x ≤ 1.2
I =
Answer key
- 1. fy(2, 2) = 1.6
- 2. fy(−1, 0.5) = 0.4244
- 3. Duf = −8
- 4. Duf = −28
- 5. I = 1.047
- 6. I = 0.4348
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