Quick help with line integrals

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The discussion revolves around calculating the line integral of the function ∫_{C}(x+yz)dx + 2xdy + xyzdz along two segments of the curve C. The first segment from (1,0,1) to (2,3,1) was computed, yielding a result of 12. The second segment from (2,3,1) to (2,5,2) was initially calculated as 55/3, but a correction pointed out that it should actually be 61/3. The total integral was incorrectly summed as 91/3, while the book states the answer is 97/3. The discussion highlights the importance of double-checking calculations in line integrals.
I dun get it
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Homework Statement


\int_{C}(x+yz)dx + 2xdy + xyzdz

C goes from (1,0,1) to (2,3,1) and (2,3,1) to (2,5,2)

The Attempt at a Solution



For C going from (1,0,1) to (2,3,1)
x=1+t, y=3t, z=1; 0\leq t \leq 1
x'(t)=1, y'(t)=3, z'(t)=0

\int^{1}_{0}(1+t+3t)*1dt + 2(1+t)*3dt + 0
=\int^{1}_{0}1+4t+6+6tdt
[7t+5t^{2}]^{1}_{0}=12



For C going from (2,3,1) to (2,5,2)
x=2, y=1+2t, z=t; 1\leq t \leq 2
x'(t)=0, y'(t)=2, z'(t)=1

\int^{2}_{1}0 + 2*2*2dt + 2(1+2t)tdt
=\int^{2}_{1}8+2t+4t^{2}dt
[8t+t^{2}+\frac{4}{3}t^{3}]^{2}_{1}=\frac{55}{3}

Total C is 12+\frac{55}{3} = \frac{91}{3}
However, the answer in the book says 97/3, so I'm not sure what I did wrong
 
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Hi I dun get it! :smile:

Your 55/3 should be 8*1 + 1*3 + (4/3)*7 = 8 + 3 + 28/3 = 61/3 :wink:
 
Question: A clock's minute hand has length 4 and its hour hand has length 3. What is the distance between the tips at the moment when it is increasing most rapidly?(Putnam Exam Question) Answer: Making assumption that both the hands moves at constant angular velocities, the answer is ## \sqrt{7} .## But don't you think this assumption is somewhat doubtful and wrong?

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