 # Conic Sections: Eccentricity

## Presentation on theme: "Conic Sections: Eccentricity"— Presentation transcript:

Conic Sections: Eccentricity
To each conic section (ellipse, parabola, hyperbola, circle) there is a number called the eccentricity that uniquely characterizes the shape of the curve.

Conic Sections: Eccentricity
If e = 1, the conic is a parabola. If e = 0, the conic is a circle. If e < 1, the conic is an ellipse. If e > 1, the conic is a hyperbola.

Conic Sections: Eccentricity
For both an ellipse and a hyperbola where c is the distance from the center to the focus and a is the distance from the center to a vertex.

Classifying Conics 10.6 What is the general 2nd degree equation for any conic? What information can the discriminant tell you about a conic?

The equation of any conic can be written in the form-
Called a general 2nd degree equation

Circles Can be multiplied out to look like this….

Ellipse Can be written like this…..

Parabola Can be written like this…..

Hyperbola Can be written like this…..

How do you know which conic it is when it’s been multiplied out?
Pay close attention to whose squared and whose not… Look at the coefficients in front of the squared terms and their signs.

Circle Both x and y are squared
And their coefficients are the same number and sign

Ellipse Both x and y are squared
Their coefficients are different but their signs remain the same.

Parabola Either x or y is squared but not both

Hyperbola Both x and y are squared
Their coefficients are different and so are their signs.

Ellipse Parabola Hyperbola Circle You Try!

When you want to be sure…
of a conic equation, then find the type of conic using discriminate information: Ax2 +Bxy +Cy2 +Dx +Ey +F = 0 B2 − 4AC < 0, B = 0 & A = C Circle B2 − 4AC < 0 & either B≠0 or A≠C Ellipse B2 − 4AC = Parabola B2 − 4AC > Hyperbola

Classify the Conic 2x2 + y2 −4x − 4 = 0 Ax2 +Bxy +Cy2 +Dx +Ey +F = 0
B2 − 4AC = 02 − 4(2)(1) = −8 B2 − 4AC < 0, the conic is an ellipse

Graph the Conic 2x2 + y2 −4x − 4 = 0 2x2 −4x + y2 = 4
V(1±√6), CV(1±√3) Complete the Square

Steps to Complete the Square
1. Group x’s and y’s. (Boys with the boys and girls with the girls) Send constant numbers to the other side of the equal sign. 2. The coefficient of the x2 and y2 must be 1. If not, factor out. 3. Take the number before the x, divide by 2 and square. Do the same with the number before y. 4. Add these numbers to both sides of the equation. *(Multiply it by the common factor in #2) 5. Factor

Write the equation in standard form by completing the square

What is the general 2nd degree equation for any conic?
What information can the discriminant tell you about a conic? B2- 4AC < 0, B = 0, A = C Circle B2- 4AC < 0, B ≠ 0, A ≠ C Ellipse B2- 4AC = 0, Parabola B2- 4AC > 0 Hyperbola

Assignment 10.6 Page 628, odd