Surface area by double integrals practice problems
Surface area of z = f(x, y) over a region, by ∬ √(1 + f_x² + f_y²) dA. 60 problems with worked solutions; in 60 of them every
equation is proved by a computer algebra system.
20 worked problems
Try each one before opening the solution. Every line is labeled with what checked it. How we verify
✓ Nihil obstat Lines: 2 proved, 2 reviewed. The answer was also checked a second way, without looking at the solution. Reviewers found nothing wrong with the explanation. The full receipt ·
How we verify
Find the area of the part of the surface \( \displaystyle z = - 3 x - 3 y + 1 \) that lies above the rectangle \( \displaystyle [0, 3] \times [0, 1] \).
Surface area = ∬ √(1 + f_x² + f_y²) dA.
Reviewed
\[ \left(\frac{\partial}{\partial x} \left(- 3 x - 3 y + 1\right)\right)^{2} + \left(\frac{\partial}{\partial y} \left(- 3 x - 3 y + 1\right)\right)^{2} + 1 = 19 \]
1 + f_x² + f_y².✓ Proved
\[ \int\limits_{0}^{1}\int\limits_{0}^{3} \sqrt{19}\, dx\, dy = 3 \sqrt{19} \]
Integrate.✓ Proved
Answer \( 3 \sqrt{19} \approx 13.07670 \)
✓ Nihil obstat Lines: 2 proved, 1 reviewed. The answer was also checked a second way, without looking at the solution. Reviewers found nothing wrong with the explanation. The full receipt ·
How we verify
Find the area of the part of the surface \( \displaystyle z = - x - 2 y + 4 \) that lies above the rectangle \( \displaystyle [0, 2] \times [0, 3] \).
Surface area = ∬ √(1 + f_x² + f_y²) dA.
Reviewed
\[ \left(\frac{\partial}{\partial x} \left(- x - 2 y + 4\right)\right)^{2} + \left(\frac{\partial}{\partial y} \left(- x - 2 y + 4\right)\right)^{2} + 1 = 6 \]
1 + f_x² + f_y².✓ Proved
\[ \int\limits_{0}^{3}\int\limits_{0}^{2} \sqrt{6}\, dx\, dy = 6 \sqrt{6} \]
Integrate.✓ Proved
Answer \( 6 \sqrt{6} \approx 14.69694 \)
✓ Nihil obstat Lines: 2 proved, 1 reviewed. The answer was also checked a second way, without looking at the solution. Reviewers found nothing wrong with the explanation. The full receipt ·
How we verify
\[ \int\limits_{0}^{2}\int\limits_{0}^{2} \sqrt{11}\, dx\, dy = 4 \sqrt{11} \]
Integrate.✓ Proved
Answer \( 4 \sqrt{11} \approx 13.26650 \)
✓ Nihil obstat Lines: 2 proved, 1 reviewed. The answer was also checked a second way, without looking at the solution. Reviewers found nothing wrong with the explanation. The full receipt ·
How we verify
Find the area of the part of the surface \( \displaystyle z = - x + 2 y - 2 \) that lies above the rectangle \( \displaystyle [0, 1] \times [0, 2] \).
Surface area = ∬ √(1 + f_x² + f_y²) dA.
Reviewed
\[ \left(\frac{\partial}{\partial x} \left(- x + 2 y - 2\right)\right)^{2} + \left(\frac{\partial}{\partial y} \left(- x + 2 y - 2\right)\right)^{2} + 1 = 6 \]
1 + f_x² + f_y².✓ Proved
\[ \int\limits_{0}^{2}\int\limits_{0}^{1} \sqrt{6}\, dx\, dy = 2 \sqrt{6} \]
Integrate.✓ Proved
Answer \( 2 \sqrt{6} \approx 4.89898 \)
✓ Nihil obstat Lines: 2 proved, 1 reviewed. The answer was also checked a second way, without looking at the solution. Reviewers found nothing wrong with the explanation. The full receipt ·
How we verify
Find the area of the part of the surface \( \displaystyle z = 3 x - y - 1 \) that lies above the rectangle \( \displaystyle [0, 1] \times [0, 1] \).
Surface area = ∬ √(1 + f_x² + f_y²) dA.
Reviewed
\[ \left(\frac{\partial}{\partial x} \left(3 x - y - 1\right)\right)^{2} + \left(\frac{\partial}{\partial y} \left(3 x - y - 1\right)\right)^{2} + 1 = 11 \]
1 + f_x² + f_y².✓ Proved
\[ \int\limits_{0}^{1}\int\limits_{0}^{1} \sqrt{11}\, dx\, dy = \sqrt{11} \]
Integrate.✓ Proved
Answer \( \sqrt{11} \approx 3.31662 \)
✓ Nihil obstat Lines: 2 proved, 1 reviewed. The answer was also checked a second way, without looking at the solution. Reviewers found nothing wrong with the explanation. The full receipt ·
How we verify
Find the area of the part of the surface \( \displaystyle z = 3 x - y + 1 \) that lies above the rectangle \( \displaystyle [0, 1] \times [0, 1] \).
Surface area = ∬ √(1 + f_x² + f_y²) dA.
Reviewed
\[ \left(\frac{\partial}{\partial x} \left(3 x - y + 1\right)\right)^{2} + \left(\frac{\partial}{\partial y} \left(3 x - y + 1\right)\right)^{2} + 1 = 11 \]
1 + f_x² + f_y².✓ Proved
\[ \int\limits_{0}^{1}\int\limits_{0}^{1} \sqrt{11}\, dx\, dy = \sqrt{11} \]
Integrate.✓ Proved
Answer \( \sqrt{11} \approx 3.31662 \)
✓ Nihil obstat Lines: 2 proved, 1 reviewed. The answer was also checked a second way, without looking at the solution. Reviewers found nothing wrong with the explanation. The full receipt ·
How we verify
Find the area of the part of the surface \( \displaystyle z = 2 x + 2 y - 2 \) that lies above the rectangle \( \displaystyle [0, 2] \times [0, 2] \).
Surface area = ∬ √(1 + f_x² + f_y²) dA.
Reviewed
\[ \left(\frac{\partial}{\partial x} \left(2 x + 2 y - 2\right)\right)^{2} + \left(\frac{\partial}{\partial y} \left(2 x + 2 y - 2\right)\right)^{2} + 1 = 9 \]
1 + f_x² + f_y².✓ Proved
\[ \int\limits_{0}^{2}\int\limits_{0}^{2} 3\, dx\, dy = 12 \]
Integrate.✓ Proved
Answer \( 12 \)
✓ Nihil obstat Lines: 2 proved, 1 reviewed. The answer was also checked a second way, without looking at the solution. Reviewers found nothing wrong with the explanation. The full receipt ·
How we verify
\[ \int\limits_{0}^{1}\int\limits_{0}^{1} \sqrt{6}\, dx\, dy = \sqrt{6} \]
Integrate.✓ Proved
Answer \( \sqrt{6} \approx 2.44949 \)
✓ Nihil obstat Lines: 2 proved, 1 reviewed. The answer was also checked a second way, without looking at the solution. Reviewers found nothing wrong with the explanation. The full receipt ·
How we verify
Find the area of the part of the surface \( \displaystyle z = 2 x - 3 y + 3 \) that lies above the rectangle \( \displaystyle [0, 1] \times [0, 1] \).
Surface area = ∬ √(1 + f_x² + f_y²) dA.
Reviewed
\[ \left(\frac{\partial}{\partial x} \left(2 x - 3 y + 3\right)\right)^{2} + \left(\frac{\partial}{\partial y} \left(2 x - 3 y + 3\right)\right)^{2} + 1 = 14 \]
1 + f_x² + f_y².✓ Proved
\[ \int\limits_{0}^{1}\int\limits_{0}^{1} \sqrt{14}\, dx\, dy = \sqrt{14} \]
Integrate.✓ Proved
Answer \( \sqrt{14} \approx 3.74166 \)
✓ Nihil obstat Lines: 2 proved, 1 reviewed. The answer was also checked a second way, without looking at the solution. Reviewers found nothing wrong with the explanation. The full receipt ·
How we verify
Find the area of the part of the surface \( \displaystyle z = - 2 x - y + 1 \) that lies above the rectangle \( \displaystyle [0, 1] \times [0, 3] \).
Surface area = ∬ √(1 + f_x² + f_y²) dA.
Reviewed
\[ \left(\frac{\partial}{\partial x} \left(- 2 x - y + 1\right)\right)^{2} + \left(\frac{\partial}{\partial y} \left(- 2 x - y + 1\right)\right)^{2} + 1 = 6 \]
1 + f_x² + f_y².✓ Proved
\[ \int\limits_{0}^{3}\int\limits_{0}^{1} \sqrt{6}\, dx\, dy = 3 \sqrt{6} \]
Integrate.✓ Proved
Answer \( 3 \sqrt{6} \approx 7.34847 \)
✓ Nihil obstat Lines: 2 proved, 1 reviewed. The answer was also checked a second way, without looking at the solution. Reviewers found nothing wrong with the explanation. The full receipt ·
How we verify
\[ \int\limits_{0}^{2}\int\limits_{0}^{2} \sqrt{3}\, dx\, dy = 4 \sqrt{3} \]
Integrate.✓ Proved
Answer \( 4 \sqrt{3} \approx 6.92820 \)
✓ Nihil obstat Lines: 2 proved, 1 reviewed. The answer was also checked a second way, without looking at the solution. Reviewers found nothing wrong with the explanation. The full receipt ·
How we verify
Find the area of the part of the surface \( \displaystyle z = - 3 x + 2 y - 2 \) that lies above the rectangle \( \displaystyle [0, 2] \times [0, 2] \).
Surface area = ∬ √(1 + f_x² + f_y²) dA.
Reviewed
\[ \left(\frac{\partial}{\partial x} \left(- 3 x + 2 y - 2\right)\right)^{2} + \left(\frac{\partial}{\partial y} \left(- 3 x + 2 y - 2\right)\right)^{2} + 1 = 14 \]
1 + f_x² + f_y².✓ Proved
\[ \int\limits_{0}^{2}\int\limits_{0}^{2} \sqrt{14}\, dx\, dy = 4 \sqrt{14} \]
Integrate.✓ Proved
Answer \( 4 \sqrt{14} \approx 14.96663 \)
✓ Nihil obstat Lines: 2 proved, 1 reviewed. The answer was also checked a second way, without looking at the solution. Reviewers found nothing wrong with the explanation. The full receipt ·
How we verify
Find the area of the part of the surface \( \displaystyle z = - x - y + 4 \) that lies above the rectangle \( \displaystyle [0, 3] \times [0, 2] \).
Surface area = ∬ √(1 + f_x² + f_y²) dA.
Reviewed
\[ \left(\frac{\partial}{\partial x} \left(- x - y + 4\right)\right)^{2} + \left(\frac{\partial}{\partial y} \left(- x - y + 4\right)\right)^{2} + 1 = 3 \]
1 + f_x² + f_y².✓ Proved
\[ \int\limits_{0}^{2}\int\limits_{0}^{3} \sqrt{3}\, dx\, dy = 6 \sqrt{3} \]
Integrate.✓ Proved
Answer \( 6 \sqrt{3} \approx 10.39230 \)
✓ Nihil obstat Lines: 2 proved, 1 reviewed. The answer was also checked a second way, without looking at the solution. Reviewers found nothing wrong with the explanation. The full receipt ·
How we verify
Find the area of the part of the surface \( \displaystyle z = - x + y - 2 \) that lies above the rectangle \( \displaystyle [0, 1] \times [0, 1] \).
Surface area = ∬ √(1 + f_x² + f_y²) dA.
Reviewed
\[ \left(\frac{\partial}{\partial x} \left(- x + y - 2\right)\right)^{2} + \left(\frac{\partial}{\partial y} \left(- x + y - 2\right)\right)^{2} + 1 = 3 \]
1 + f_x² + f_y².✓ Proved
\[ \int\limits_{0}^{1}\int\limits_{0}^{1} \sqrt{3}\, dx\, dy = \sqrt{3} \]
Integrate.✓ Proved
Answer \( \sqrt{3} \approx 1.73205 \)
✓ Nihil obstat Lines: 2 proved, 1 reviewed. The answer was also checked a second way, without looking at the solution. Reviewers found nothing wrong with the explanation. The full receipt ·
How we verify
\[ \int\limits_{0}^{1}\int\limits_{0}^{1} \sqrt{3}\, dx\, dy = \sqrt{3} \]
Integrate.✓ Proved
Answer \( \sqrt{3} \approx 1.73205 \)
✓ Nihil obstat Lines: 2 proved, 1 reviewed. The answer was also checked a second way, without looking at the solution. Reviewers found nothing wrong with the explanation. The full receipt ·
How we verify
\[ \int\limits_{0}^{1}\int\limits_{0}^{2} \sqrt{3}\, dx\, dy = 2 \sqrt{3} \]
Integrate.✓ Proved
Answer \( 2 \sqrt{3} \approx 3.46410 \)
✓ Nihil obstat Lines: 2 proved, 1 reviewed. The answer was also checked a second way, without looking at the solution. Reviewers found nothing wrong with the explanation. The full receipt ·
How we verify
\[ \int\limits_{0}^{2}\int\limits_{0}^{2} \sqrt{3}\, dx\, dy = 4 \sqrt{3} \]
Integrate.✓ Proved
Answer \( 4 \sqrt{3} \approx 6.92820 \)
✓ Nihil obstat Lines: 2 proved, 1 reviewed. The answer was also checked a second way, without looking at the solution. Reviewers found nothing wrong with the explanation. The full receipt ·
How we verify
\[ \int\limits_{0}^{3}\int\limits_{0}^{3} \sqrt{6}\, dx\, dy = 9 \sqrt{6} \]
Integrate.✓ Proved
Answer \( 9 \sqrt{6} \approx 22.04541 \)
✓ Nihil obstat Lines: 2 proved, 1 reviewed. The answer was also checked a second way, without looking at the solution. Reviewers found nothing wrong with the explanation. The full receipt ·
How we verify
Find the area of the part of the surface \( \displaystyle z = 2 x + y + 2 \) that lies above the rectangle \( \displaystyle [0, 1] \times [0, 1] \).
Surface area = ∬ √(1 + f_x² + f_y²) dA.
Reviewed
\[ \left(\frac{\partial}{\partial x} \left(2 x + y + 2\right)\right)^{2} + \left(\frac{\partial}{\partial y} \left(2 x + y + 2\right)\right)^{2} + 1 = 6 \]
1 + f_x² + f_y².✓ Proved
\[ \int\limits_{0}^{1}\int\limits_{0}^{1} \sqrt{6}\, dx\, dy = \sqrt{6} \]
Integrate.✓ Proved
Answer \( \sqrt{6} \approx 2.44949 \)
✓ Nihil obstat Lines: 2 proved, 1 reviewed. The answer was also checked a second way, without looking at the solution. Reviewers found nothing wrong with the explanation. The full receipt ·
How we verify