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# In Exercises $43 - 46 ,$ use a CAS to perform the following steps to evaluate the line integrals.$$\begin{array} { l } { \text { a. Find } d s = | \mathbf { v } ( t ) | d t \text { for the path } \mathbf { r } ( t ) = g ( t ) \mathbf { i } + h ( t ) \mathbf { j } + k ( t ) \mathbf { k } \text { . } } \\ { \text { b. Express the integrand } f ( g ( t ) , h ( t ) , k ( t ) ) | \mathbf { v } ( t ) | \text { as a function of the parameter } t . } \\ { \text { c. Evaluate } \int _ { C } f d s \text { using Equation } ( 2 ) \text { in the text. } } \end{array}$$$$\begin{array} { l } { f ( x , y , z ) = \sqrt { 1 + 30 x ^ { 2 } + 10 y } ; \quad \mathbf { r } ( t ) = t \mathbf { i } + t ^ { 2 } \mathbf { j } + 3 t ^ { 2 } \mathbf { k } } \\ { 0 \leq t \leq 2 } \end{array}$$

## A. $d s=\left(\sqrt{1+40 t^{2}}\right) d t$B. $f(g(t), h(t), k(t))|v(t)|=\left(\sqrt{1+40 t^{2}}\right)\left(\sqrt{1+40 t^{2}}\right)$C. $\int_{C} f \cdot d s \approx 108.67$

Integrals

Vectors

Vector Functions

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##### Lily A.

Johns Hopkins University

##### Samuel H.

University of Nottingham

##### Michael J.

Idaho State University

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### Video Transcript

Okay. What we want to do is we want to, um right or find, um we went to find d s, which is equal to V of tea. Um, de ti four, um, r of t is equal to t I plus t square J plus three t squared. Okay, um and so we know that the, uh t is equal to the derivative, which is gonna be a plus to TJ plus six t k. And so, um, the magnitude is gonna be the square root of one squared plus two t squared plus 60 squared, which is gonna give me the square root of one plus 40 t squared. And so D s is equal to the square root of one plus 40 t squared TT. Okay. And then now we want to express, um, the in a grand of our function. And our function is X Y Z is equal to the square root of one plus 30 x squared plus 10. Why and t goes from 0 to 2 inclusive. And so my inner role is going to be from 0 to 2. Ah, my function in terms of tea. And so we know exes. T so I would have a 30 t squared there plus a And I know why is T squares or a 10 T squared? So this would be a one plus 40 t square times d s, which is a one plus 40 t squared TT. So here is my integral. And now what we want to do is we want to go ahead and use a, um either a online, um, calculator or your calculator to actually evaluate this integral. And so I'm gonna go ahead, um, and pull up. I haven't 84 plus emulator. And so what we're gonna do is we're going to evaluate that integral using the calculator. So on mine, I go to math and I go all the way down here to function integration. And I'm going from zero 22 and I have the square root. But I noticed Now, couple things we can knows that we have a square root of one place for a t square times another one, which means, um, this is just going to be a one plus a 40. And unfortunately, I'm gonna have to use X squared in here. Um, and then I'm integrating. Um, not with respect to Esso, with respect to ask X and hit enter. So I get 108.67 So this is actually equal to, um 100 and eight 0.67

University of Central Arkansas

#### Topics

Integrals

Vectors

Vector Functions

##### Lily A.

Johns Hopkins University

##### Samuel H.

University of Nottingham

##### Michael J.

Idaho State University

Lectures

Join Bootcamp