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Identifying Conic Sections. How do I determine whether the graph of an equation represents a conic, and if so, which conic does it represent, a circle, an ellipse, a parabola or a hyperbola?. We usually see conic equations written in General, or Implicit Form:.
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Identifying Conic Sections How do I determine whether the graph of an equation represents a conic, and if so, which conic does it represent, a circle, an ellipse, a parabola or a hyperbola?
We usually see conic equations written in General, or Implicit Form: General Form of a Conic Equation where A, B, C, D, E and F are integers and A, B and C are NOT ALL equal to zero. Note: You may see some conic equations solved for y, but if the equation can be re-written into the form above, it is a conic equation!
Please Note: A conic equation written in General Form doesn’t have to have all SIX terms! Several of the coefficients A, B, C, D, E and F can equal zero, as long as A, B and C don’t ALL equal zero. If A, B and C all equal zero, what kind of equation do you have? ... T H I N K... Linear!
So, it’s a conic equation if... • the highest degree (power) of x and/or y is 2 (at least ONE has to be squared) • the other terms are either linear, constant, or the product of x and y • there are no variable terms with rational exponents (i.e. no radical expressions) or terms with negative exponents (i.e. no rational expressions)
The values of the coefficients in the conic equation determine the TYPE of conic. What values form an Ellipse? What values form a Circle? What values form a Hyperbola? What values form a Parabola?
Ellipses... where A & C have the SAME SIGN NOTE: There is noBxy term, and D, E & Fmay equal zero! For example:
Ellipses…a special case! When A & C are the samevalue as well as the same sign, the ellipse is the same length in all directions … Circle! it is a ...
Hyperbola... where A & C have DIFFERENT signs. NOTE: There is noBxy term, and D, E & Fmay equal zero! For example:
A parabola is vertical if the equation has an x squared term AND a linear y term; it may or may not have a linear x term & constant: A parabola is horizontal if the equation has a y squared term AND a linear x term; it may or may not have a linear y term & constant: Parabola... A Parabola can be oriented 2 different ways:
Parabola …Vertical The following equations all represent vertical parabolas in general form; they all have a squared x term and a linear y term:
Parabola …Horizontal The following equations all represent horizontal parabolas in general form, they all have a squared y term and a linear x term:
where A, B, C, D, E and F are integers and A, B and C are NOT ALL equal to zero. Summary ... General Form of a Conic Equation: Identifying a Conic Equation:
Practice ... Identify each of the following equations as a(n): (a) ellipse (b) circle (c) hyperbola (d) parabola (e) not a conic _____________________________________________________
Answers ... (a) ellipse (b) circle (c) hyperbola (d) parabola (e) not a conic • 1) ellipse • 2) hyperbola • 3) parabola • 4) circle • 5) ellipse • 6) not a conic • 7) parabola • 8) hyperbola
P H Conic Sections ! C E