9.1-9.5 Flashcards
Standard form of a circle with center at origin
x2+y2=r2
Write an equation of circle with a point
Plug in x and y
Solve
Steps to write an equation of a line tangent to the circle
Find slope of radius to point, (0,0) to point
Find slope of tangent (radical of slope)
Use point slope form to find the equation of the tangent line or y=mx+b
Major axis
Longer axis
Contains Foci
Ends with vertices
Minor axis
Shorter axis
Contains covertices
A
B
C
In ellipses
A-vertices
B-covertices
C-foci
Horizontal major ellipse equation
X2/a2 + y2/b2= 1
Horizontal major ellipse vertices and covertices equation
Vertices (+- a,0)
Covertices (0,+-b)
A away
B away
Vertical major ellipse equation
X2/b2 + y2/a2= 1
Vertical major ellipse vertices and covertices
Vertices (0,+-a)
Covertices (+-b,0)
How to find foci of ellipse
C UNITs from the center on the major axis
c2=a2-b2
For ellipse A goes under
Which ever axis is the major axis
Distance formula
D=|(x-x)2 + (y-y)2
Midpoint formula
(x+x/2, y+y/2)
To find a perpendicular busector
Find midpoint of segment
Find the slope of segment
Find slope of perpendicular line
Use y=mx+b to form equation with perpendicular slope and midpoint
Directrix
The perpendicular line to parabola
Any point on a parabola is —– to focus point and directrix
Equal distance
X=y2 parabola
Opens to side