MHB Slope of Tangent line to Polar curve

JProgrammer
Messages
20
Reaction score
0
I am trying to find the slope of the tangent line of this polar equation:

r = 4 + sin theta, (4,0)

I put the equation into wolfram alpha and it gives me a 3D plot.

If someone could help me find the slope of the tangent line, I would really appreciate it.
Thank you.
 
Physics news on Phys.org

Attachments

  • 120norr.jpg.png
    120norr.jpg.png
    8.2 KB · Views: 101
Last edited by a moderator:
JProgrammer said:
I am trying to find the slope of the tangent line of this polar equation:

r \:=\: 4 + \sin\theta\;\; (4,0)
Here is the derivation of the formula you want.

\begin{array}{cccccc}<br /> y \;=\;r\sin\theta &amp; \Rightarrow &amp; \dfrac{dy}{d\theta} \;=\;r\cos\theta + r&#039;\sin\theta \\<br /> x \;=\;r\cos\theta &amp; \Rightarrow &amp; \;\;\dfrac{dx}{d\theta} \;=\;-r\sin\theta + r&#039;\cos\theta \end{array}

\text{Therefore: }\;\frac{dy}{dx} \;=\;\dfrac{\dfrac{dy}{d\theta}}{\dfrac{dx}{d\theta}} \;=\; \dfrac{r\cos\theta + r&#039;\sin\theta}{-r\sin\theta + r&#039;\cos\theta}\text{For this problem: }\;r \:=\:4 + \sin\theta,\;r&#039; \:=\:\cos\theta

\text{We have: }\;\dfrac{dy}{dx} \;=\;\dfrac{(4+\sin\theta)\cos\theta + \cos\theta\sin\theta}{-(4+\sin\theta)\sin\theta + \cos\theta\cos\theta}

Now substitute \theta = 0.
 
Back
Top