- #1
mdawg467
- 14
- 0
Homework Statement
Consider the plane curve [tex] \overrightarrow{r(t)}=e^tcost(t)\hat{i}+e^tsin(t) \hat{j}[/tex]
Find the following when t= ∏/2
[tex] Part A: \hat{T}(t)[/tex]
[tex] Part B: \hat{B}(t)[/tex]
[tex] Part C: \hat{N}(t)[/tex]
Homework Equations
[tex] \hat{N}(t)=\frac{\hat{T}(t)}{||\hat{T}(t)||}[/tex]
[tex] \hat{T}(t)=\frac{\overrightarrow{r'(t)}}{|| \overrightarrow{r'(t)}||}[/tex]
[tex]\hat{B(t)}=\frac{\overrightarrow{r'(t)\times r''(t) }}{||\overrightarrow{r'(t)\times r''(t)}||}[/tex]
The Attempt at a Solution
Part A
[tex]\overrightarrow{r(t)}=e^tcost(t)\hat{i}+e^tsin(t) \hat{j} [/tex]
[tex] \overrightarrow{r'(t)}=e^t[(cos(t)-sin(t))\hat{i} \:+\:(sin(t)+cos(t))\hat{j}] [/tex]
[tex] \overrightarrow{r'(\frac{\pi }{2})}=e^\frac{\pi }{2}[(cos(\frac{\pi }{2})-sin(\frac{\pi }{2}))\hat{i} \:+\:(sin(\frac{\pi }{2})+cos(\frac{\pi }{2}))\hat{j}] [/tex]
[tex] \overrightarrow{r'(\frac{\pi }{2})}=-e^\frac{\pi }{2}\hat{i}\;+\;e^\frac{\pi }{2}\hat{j} [/tex]
[tex]\hat{T}(t) =\frac{-e^\frac{\pi }{2}\hat{i}\;+\;e^\frac{\pi }{2}\hat{j}}{ \sqrt{(-e^\frac{\pi }{2})^2\;+\;(e^\frac{\pi }{2})^2} }[/tex]
Based off of Part A, plugging the numbers into Part B and C generate:
[tex]\hat{B(t)}=\frac{\overrightarrow{r'(t)\times r''(t) }}{||\overrightarrow{r'(t)\times r''(t)}||}=0[/tex]
[tex] \hat{N}(t)=\frac{\hat{T}(t)}{||\hat{T}(t)||}=0[/tex]
Not sure if I solved this correctly.
Any help would be great. Thank you.