Calculus 8th Edition

Published by Cengage
ISBN 10: 1285740629
ISBN 13: 978-1-28574-062-1

Chapter 10 - Parametric Equations and Polar Coordinates - Review - Concept Check - Page 729: 5

Answer

(a) The slope of the tangent line to a polar curve is defined as $$\frac{dy}{dx}$$. Slope in terms of polar coordinates can be wtriiten as $$\dfrac{dy/dθ}{dx/dθ} = \dfrac{\frac{d}{dθ}(rsin(θ))}{\frac{d}{dθ}(rcos(θ))}=\frac{\frac{d}{dθ}(sin(θ)+rcos(θ))}{\frac{d}{dθ}(cos(θ)-rsin(θ))}$$ (b) Area of a region bounded by a polar curve is defined as $$A=\int_{a}^{b} \frac{1}{2}r^{2}dθ$$ (c) Length of a polar curve can be expreesed as: $$L= \int_{a}^{b} \sqrt ((\frac{dx}{dθ})^{2}+(\frac{dy}{dθ})^{2})dθ= \int_{a}^{b} \sqrt (r^{2}+(\frac{dr}{dθ})^{2})dθ$$

Work Step by Step

(a) The slope of the tangent line to a polar curve is defined as $$\frac{dy}{dx}$$. Slope in terms of polar coordinates can be wtriiten as $$\dfrac{dy/dθ}{dx/dθ} = \dfrac{\frac{d}{dθ}(rsin(θ))}{\frac{d}{dθ}(rcos(θ))}=\frac{\frac{d}{dθ}(sin(θ)+rcos(θ))}{\frac{d}{dθ}(cos(θ)-rsin(θ))}$$ (b) Area of a region bounded by a polar curve is defined as $$A=\int_{a}^{b} \frac{1}{2}r^{2}dθ$$ (c) Length of a polar curve can be expreesed as: $$L= \int_{a}^{b} \sqrt ((\frac{dx}{dθ})^{2}+(\frac{dy}{dθ})^{2})dθ= \int_{a}^{b} \sqrt (r^{2}+(\frac{dr}{dθ})^{2})dθ$$
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