Unformatted text preview: and y :
• the xintercepts always have the form (x, 0); to ﬁnd the xintercepts of the graph, set y = 0
and solve for x.
• y intercepts always have the form (0, y ); to ﬁnd the y intercepts of the graph, set x = 0 and
solve for y .
Another fact which you may have noticed about the graph in the previous example is that it seems
to be symmetric about the y axis. To actually prove this analytically, we assume (x, y ) is a generic
point on the graph of the equation. That is, we assume x2 + y 3 = 1. As we learned in Section 1.1,
the point symmetric to (x, y ) about the y axis is (−x, y ). To show the graph is symmetric about
the y axis, we need to show that (−x, y ) is on the graph whenever (x, y ) is. In other words, we
need to show (−x, y ) satisﬁes the equation x2 + y 3 = 1 whenever (x, y ) does. Substituting gives
? (−x)2 + (y )3 = 1
x2 + y 3 = 1
When we substituted (−x, y ) into the equation x2 + y 3 = 1, we obtained the original equation back
when we simpliﬁed. Th...
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 Fall '13
 Wong
 Algebra, Trigonometry, Cartesian Coordinate System, The Land, The Waves, René Descartes, Euclidean geometry

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