KnightsPG
04-22-2002, 02:24 PM
This questions comes from the Averbach-Mehta study guide, practice exam 3, question # 32
A curve in R^3 has parametric equations x = 2(t^1.5), y = 2t + 1, z = squareroot 3 * t. Calculate the length of the curve between the points corresponding to t = 1, t = 2.
My answer follows the answer key until we get to the integral from 1 to 2 of squareroot of 9t + 7.
I use substitution: u = 9t + 7. du = 9, hence we have...
step 1: integral from 16 to 25 of squareroot u times 1/9
step 2: 2(u^1.5)/27 evaluated from 16 to 25
step 3: 250/27 - 64/27 = 186/27 = 62/9
The answer key gives an answer of 122/27. Can anyone help me out? Am I working through the steps of substitution wrong?
Thanks!
A curve in R^3 has parametric equations x = 2(t^1.5), y = 2t + 1, z = squareroot 3 * t. Calculate the length of the curve between the points corresponding to t = 1, t = 2.
My answer follows the answer key until we get to the integral from 1 to 2 of squareroot of 9t + 7.
I use substitution: u = 9t + 7. du = 9, hence we have...
step 1: integral from 16 to 25 of squareroot u times 1/9
step 2: 2(u^1.5)/27 evaluated from 16 to 25
step 3: 250/27 - 64/27 = 186/27 = 62/9
The answer key gives an answer of 122/27. Can anyone help me out? Am I working through the steps of substitution wrong?
Thanks!