Arc length problem

mj.c

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Aug 6, 2021
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Consider the curve given by [math]e^x = y^3 + 10[/math]a. Set up an integral in terms of x that represents the arclength from x = 1 to x = 2. Then evaluate your integral using a computer system.
b. Set up an integral in terms of y that represents the arclength from x = 1 to x = 2. then evaluate your integral using a computer system and make sure it matches with part a.

My answers:
a. I isolated y to get [math]y = cuberoot(e^x - 10)[/math] Then I took the derivative of that to get e^x / (3(e^x-10)^(2/3). My integrand for the definite integral from 1 to 2 was then sqrt(1 + (e^x / (3(e^x - 10))^2/3)^2). Inputting this into integral-calculator.com, it said that there was no elementary antiderivative but that the approximation was 1.169606600612212. Is this correct?

b. I isolated x to get [math]x = ln(y^3 + 10)[/math] Then I took the derivative of that and got [math]3y^2/(y^3+10)[/math]. Then my integrand was sqrt(1+(3y^2/(y^3 + 10))^2). Inputting this into integral-calculator.com, it said that there was no elementary antiderivative but that the approximation was 1.119682131946315. The two answers are not the same, but since they're approximations, is this correct anyways? Was my process on both of these correct to begin with or am I making a mistake somewhere? Thank you!
 
I get the same result you get to several decimals using Maple. I also get the same result for the second part. I'm guessing you may have used the wrong limits in your dy integral. You need to use the values of y that give x =1 and x=2 for your y limits.
 
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