Let


Then we have the followings.
Distance

Midpoint

of

and

Standard Equation of circle, center at

and radius


Determine if a graph represents a function.
Method 1: Recall that we can use the vertical line test to check if a graph represents a function.
Method 2: Given an equation, if

can be expressed in terms of

then the graph represents a function. The graphs of the following examples
represent functions.




Exercises:
Given the following points

and

find (a) the distance of

and

(b) midpoint of

(c) the standard equation of the circle which uses

as its diameter.






Given the following equations, if it is circle, find its center and radius. If it is not a circle, explains why.

[center

and radius


[center

radius


[this is not a circle, why?]

[ this is a point, (3,2) which is the center.]

[ this does not represent a graph, the left hand side of the equation is
positive, but the right hand side is negative.]
Given

and

Find
the corresponding points

and

if

and

are being shifted left

units and down

units. Repeat the process by using the points

and

from Questions 1 to 4 above.