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# Find Unit Tangent Vector at Given Point

MVCALC-NW2GAY

Let:

$${\bf r}(t)=\sin t {\bf i} + t {\bf j} +cos t {\bf k}$$

What is the unit tangent vector of ${\bf r}(t)$ at the point $P=(0,\pi,-1)$?

A

$\frac{1}{\sqrt{2}}{\bf j} + \frac{1}{\sqrt{2}}{\bf k}$

B

$\frac{1}{\sqrt{2}}{\bf i} + \frac{1}{\sqrt{2}}{\bf k}$

C

$-\frac{1}{\sqrt{2}}{\bf i} + \frac{1}{\sqrt{2}}{\bf k}$

D

$-\frac{1}{\sqrt{2}}{\bf j} + \frac{1}{\sqrt{2}}{\bf k}$

E

$-\frac{1}{\sqrt{2}}{\bf i} + \frac{1}{\sqrt{2}}{\bf j}$