Find the definite integral of a vector

[professordad]

Homework Statement

If [itex]\vec{r}(t) = t^2\vec{i} + t\cos{(\pi t)}\vec{j} + \sin{(\pi t)}\vec{k}[/itex], evaluate [itex]\int_{0}^{1} \vec{r}(t) \text{dt}[/itex].

Homework Equations

The Attempt at a Solution

So I tried integrating each individual part, and I got
[itex]\frac{1}{3}t^3\vec{i} + (-\pi t\sin{(\pi t)} - \frac{\sin{(\pi t)}}{\pi})\vec{j} - \frac{\cos{(\pi t)}}{t}\vec{k} |_{0}^{1}[/itex]
(For the coefficient of [itex]\vec{j}[/itex] I used integration by parts, I'm not sure if that's right because it looks weird)
But evaluating at 0 makes the coefficient of [itex]\vec{k}[/itex] undefined! What should I do? Thanks.

 

[SammyS]

Homework Statement

If [itex]\vec{r}(t) = t^2\vec{i} + t\cos{(\pi t)}\vec{j} + \sin{(\pi t)}\vec{k}[/itex], evaluate [itex]\int_{0}^{1} \vec{r}(t) \text{dt}[/itex].

Homework Equations

The Attempt at a Solution

So I tried integrating each individual part, and I got
[itex]\frac{1}{3}t^3\vec{i} + (-\pi t\sin{(\pi t)} - \frac{\sin{(\pi t)}}{\pi})\vec{j} - \frac{\cos{(\pi t)}}{t}\vec{k} |_{0}^{1}[/itex]
(For the coefficient of [itex]\vec{j}[/itex] I used integration by parts, I'm not sure if that's right because it looks weird)
But evaluating at 0 makes the coefficient of [itex]\vec{k}[/itex] undefined! What should I do? Thanks.

You do realize that

[itex]\displaystyle
\int_{0}^{1} \vec{r}(t)\,dt=\hat{i}\int_{0}^{1} t^2\,dt+\hat{j}\int_{0}^{1} t\cos(\pi t)\,dt- \hat{k}\int_{0}^{1} \sin(\pi t)\,dt\ ,[/itex]​

don't you?

Show how you did the integration by parts, and show how you get a t in the denominator of the k component.