For f(x, y) = 3 ln(x² + 4y²), find the partial derivative ∂f/∂y at the point (1, 2).
Multivariable calculus worksheet with answers
1.Easy
f(x, y) = 3 ln(x² + 4y²)P = (1, 2)
fy(1, 2) =
2.Easy
For f(x, y) = sin(2x − y), find the partial derivative ∂f/∂x at the point (1, −1).
f(x, y) = sin(2x − y)P = (1, −1)
fx(1, −1) =
3.Medium
For f(x, y) = −y·e3xy, find the directional derivative Duf at (−1, 0.5) in the direction of v = (3, −1).
f(x, y) = −y·e3xyP = (−1, 0.5)v = (3, −1)
Duf =
4.Medium
For f(x, y) = 2 sin(−2x − 3y), find the directional derivative Duf at P(1, −1) in the direction towards Q(3, 2).
f(x, y) = 2 sin(−2x − 3y)P = (1, −1)Q = (3, 2)
Duf =
5.Hard
Evaluate I = ∬R y dA, where R is the region between the parabola y = x² and the line y = 3x.
y = x²y = 3xf = y
I =
6.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 =
Answer key
- 1. fy(1, 2) = 2.824
- 2. fx(1, −1) = −1.98
- 3. Duf = −0.194
- 4. Duf = −3.896
- 5. I = 16.2
- 6. I = 1.047
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