Chapter 10: Problem 72
Find a polar equation for each conic section. Assume one focus is at the origin.
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Chapter 10: Problem 72
Find a polar equation for each conic section. Assume one focus is at the origin.
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A focal chord of a conic section is a line through a focus joining two points of the curve. The latus rectum is the focal chord perpendicular to the major axis of the conic. Prove the following properties. The length of the latus rectum of an ellipse centered at the origin is \(2 b^{2} / a=2 b \sqrt{1-e^{2}}\)
Find an equation of the following curves, assuming the center is at the origin. Sketch a graph labeling the vertices, foci, asymptotes (if they exist), and directrices. Use a graphing utility to check your work. An ellipse with vertices (±9,0) and eccentricity \(\frac{1}{3}\)
Completed in 1937, San Francisco's Golden Gate Bridge is \(2.7 \mathrm{km}\) long and weighs about 890,000 tons. The length of the span between the two central towers is \(1280 \mathrm{m}\) the towers themselves extend \(152 \mathrm{m}\) above the roadway. The cables that support the deck of the bridge between the two towers hang in a parabola (see figure). Assuming the origin is midway between the towers on the deck of the bridge, find an equation that describes the cables. How long is a guy wire that hangs vertically from the cables to the roadway \(500 \mathrm{m}\) from the center of the bridge?
Prove that the equations $$x=a \cos t+b \sin t, \quad y=c \cos t+d \sin t,$$ where \(a, b, c,\) and \(d\) are real numbers, describe a circle of radius \(R\) provided \(a^{2}+c^{2}=b^{2}+d^{2}=R^{2}\) and \(a b+c d=0.\)
Find parametric equations (not unique) of the following ellipses (see Exercises \(75-76\) ). Graph the ellipse and find a description in terms of \(x\) and \(y.\) An ellipse centered at the origin with major and minor axes of lengths 12 and \(2,\) on the \(x\) - and \(y\) -axes, respectively, generated clockwise
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