PRE-CALCULUS
SIR JOSEPH
Specific objectives:
• illustrate the different types of conic sections: parabola, ellipse,
circle, hyperbola, and degenerate cases
• define a circle
• determine the standard form of equation of a circle
• graph a circle in a rectangular coordinate system
CONIC SECTIONS
A conic section, or simply conic, is a curve formed by the
intersection of a plane and a double right circular cone.
CONIC SECTIONS
A conic section, or simply conic, is a curve formed by the
intersection of a plane and a double right circular cone.
Circle
1
TYPESOF CONIC SECTIONS
Ellipse
2
Parabola
Hyperbola
3
4
TYPESOF CONIC SECTIONS
• Circle - the cutting plane is not parallel to any generator but is perpendicular to the axis
TYPESOF CONIC SECTIONS
• Ellipse- the cutting plane is not parallel to any generator
TYPESOF CONIC SECTIONS
• Parabola- the cutting plane is parallel to one and only one generator
TYPESOF CONIC SECTIONS
• Hyperbola- the cutting plane is parallel to the axis of the double cone
- is perpendicular to the bases of the two cones
TYPESOF CONIC SECTIONS
• Circle
• Ellipse
• Parabola
• Hyperbola
TYPESOF CONIC SECTIONS
• Circle
• Ellipse
• Parabola
• Hyperbola
Point
1
2
Line
3
Intersecting lines
DEGENERATE CASES:
DEGENERATECASES:
• Point - the cutting plane passes through the vertex of the cone
DEGENERATECASES:
• Line - the cutting plane passes through the generators
DEGENERATECASES:
• Intersecting lines - the cutting plane passes through the axis
DEGENERATECASES:
• Point
• Line
• Intersecting lines
DEGENERATECASES:
• Point
• Line
• Intersecting lines
KEY ELEMENTS:
• focus (F) - the fixed point of the conic
• directrix (d) - the fixed line d corresponding to the focus
• principal axis (a) - the line that passes through the focus and
perpendicular to the directrix
• vertec (V) - the point of intersection of the conic and its principal
• eccentricity (e) - the constant ratio
KEY ELEMENTS:
CIRCLE
A circle is a set of all coplanar points such that the distance
from a fixed point is constant. The fixed point is called the center of
the cicle and the constant distance form the center is called the
radius of the circle.
EQUATION OF A CIRCLE
Given that (h, k) is the center of the circle;
and (x, y) is a point in the circle
(x - h) 2 +(y - k)2
r
(x - h) 2 +(y - k)2
r
r2 = (x - h) 2 +(y - k)2
(x - h) 2 +(y - k)2 =r2
Standard form
EQUATION OF A CIRCLE
(x - h) 2 +(y - k)2 =r2
General form
x 2 +y 2 +Ax +By+C=0
Standard form
EQUATION OF A CIRCLE
To derive the equation of a circle whose center C is at the point (0, 0)
and with radius r, let P(x, y) be one of the points on the circle.
(x - 0) 2 +(y - 0)2
r
(x - 0) 2 +(y - 0)2
r
r2 = (x)2 +(y)2
r2 = x2 +y2
EXAMPLES:
Determine the standard form of equation of the circle given its
center and radius.
a. center (0, 0) , radius = 4
b. center (2, 5) , radius = 6
c. center (-2, 7) , radius = 4
d. center (-8, -5) , radius = 3
EXAMPLE a.:
center (0, 0) , radius =4
(x - h) 2 +(y - k)2 =r2
EXAMPLE A:
center (2, 5) , radius =6
(x - h) 2 +(y - k)2 =r2
EXAMPLE B:
center (2, 5) , radius =6
(x - h) 2 +(y - k)2 =r2 x 2 +y 2 +Ax +By+C=0
EXAMPLE C:
center (-2, 7) , radius =4
(x - h) 2 +(y - k)2 =r2
EXAMPLE D:
center (-8, -5) , radius =3
(x - h) 2 +(y - k)2 =r2
QUIZ:
Write the equation of the circle in general form and in standard
form.
1. center (3, -2) , radius =4
2. center (6, 5) , radius =8
3. center (0, 8), radius =1
1
(x - h) 2 +(y - k)2 =r2
x 2 +y 2 +Ax +By+C=0
THANK YOU
May GOD bless you always!

pre-cal first topic.pptx/PRE-CAL/PPTX.123