Question 1
Consider an object moving along the parametrized curve with equations:
x(t) = eᵗ + e⁻ᵗ
y(t) = eᵗ - e⁻ᵗ
where t is in the time interval [0,4] seconds.
Fill in the blanks:
The maximum speed of the object on the time interval is 5.458 at time t = 4.
The minimum speed of the object on the time interval is 0.991 at time t = ¼ ln 2.
Question 2
Find the exact length of the curve:
y = √(x - x²) + sin⁻¹√x
Answer
To find the exact length:
Parameterize x = sin²u
Derive dy/du and dx/du
Combine:
(
𝑑
𝑠
/
𝑑
𝑢
)
2
=
(
𝑑
𝑥
/
𝑑
𝑢
)
2
+
(
𝑑
𝑦
/
𝑑
𝑢
)
2
=
4
𝑐
𝑜
𝑠
2
𝑢
(ds/du)
2
=(dx/du)
2
+(dy/du)
2
=4cos
2
u
Exact length of the curve: 2
Question 3
Evaluate the iterated integral by converting to polar coordinates:
∫₀² ∫₀√(2x - x²) xy dy dx
Answer
Convert to polar coordinates:
𝐼
=
∫
0
(
𝜋
/
2
)
∫
0
2
𝑟
3
𝑐
𝑜
𝑠
2
(
𝜃
)
𝑠
𝑖
𝑛
(
𝜃
)
𝑑
𝑟
𝑑
𝜃
I=∫
0
(
π/2)∫
0
2
r
3
cos
2
(θ)sin(θ)drdθ
Solving:
Result: 2/3
Question 4
Find the volume of the given solid. The tetrahedron enclosed by the coordinate planes and the plane 2x + y + z = 4.
Answer
The region is bounded by:
∫
0
2
∫
0
(
4
−
2
𝑥
)
∫
0
(
4
−
2
𝑥
−
𝑦
)
𝑑
𝑧
𝑑
𝑦
𝑑
𝑥
∫
0
2
∫
0
(
4−2x)∫
0
(
4−2x−y)dzdydx
Integrating gives the volume.
Question 5
Find the exact length of the curve:
Y = y⁴/8 + 1/(4y²), 1 ≤ y ≤ 2
Answer
Using:
𝐿
=
∫
1
2
1
+
(
𝑑
𝑌
𝑑
𝑦
)
2
𝑑
𝑦
L=∫
1
2
1+(
dy
dY
)
2
dy
Simplify derivatives and solve:
Result expressed in terms of y for final length.
Integrals #6 - Questions and Answers
of 6
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