Stitz-Zeager_College_Algebra_e-book

Our solution is 2 1 substituting x 2 and y 1 into the

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Unformatted text preview: 1 in Definition 7.2. Replacing x with (x − h) and y with (y − k ) causes the usual horizontal and vertical shifts. Replacing x with x and y with y a b causes the usual vertical and horizontal stretches. In other words, it is perfectly fine to think of an ellipse as the deformation of a circle in which the circle is stretched farther in one direction than the other. (x + 1)2 (y − 2)2 Example 7.4.1. Graph + = 1. Find the center, the lines which contain the major 9 25 and minor axes, the vertices, and the foci. Solution. We see that this equation is in the standard form of Equation 7.4. Here x − h is x + 1 so h = −1, and y − k is y − 2 so k = 2. Hence, our ellipse is centered at (−1, 2). We see that a2 = 9 so a = 3, and b2 = 25 so b = 5. This means that we move 3 units left and right from the center and 5 units up and down from the center to arrive at points on the ellipse. As an aid to sketching, we draw a rectangle matching this description, called a guide rectangle, and sketch the ellipse inside this rectangle as seen below on the left. 7.4 Ellipses 423 y y 7 6 4 3 3 2 2 1 −2 5 4 3 6 5 −4 7 1 −1 1 2 ...
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This note was uploaded on 05/03/2013 for the course MATH Algebra taught by Professor Wong during the Fall '13 term at Chicago Academy High School.

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