MHB Slope of Tangent line to Polar curve

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To find the slope of the tangent line for the polar equation r = 4 + sin(θ) at the point (4,0), the derivative formula is used. The derivatives dy/dθ and dx/dθ are derived from the polar coordinates, leading to the formula dy/dx = (r cos(θ) + r' sin(θ)) / (-r sin(θ) + r' cos(θ)). Substituting r = 4 + sin(θ) and r' = cos(θ) into this formula yields a specific expression for the slope. Finally, substituting θ = 0 into the equation provides the slope of the tangent line at the given point.
JProgrammer
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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.
 
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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.
 
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