1. Continuity
Section 2.3a

2. Find the points at which the function f is continuous, and the
points at which f is discontinuous.
In general, a continuous
function is a function whose
outputs vary continuously with
the inputs and do not “jump”
from one value to another
without taking on values in
between.
Graphically, any function f(x) whose graph can be sketched in
one continuous motion without lifting the pencil is an example
of a continuous function…

3. Find the points at which the function f is continuous, and the
points at which f is discontinuous.
The function f is continuous at
every point in its domain [0,4]
except at x = 1 and x = 2. Note
the relationship between the
limit of f and the value of f at
each point of the function’s
domain.
Points at which f is continuous:
At x = 0,
At x = 4,
At 0 < c < 4,

4. Find the points at which the function f is continuous, and the
points at which f is discontinuous.
The function f is continuous at
every point in its domain [0,4]
except at x = 1 and x = 2. Note
the relationship between the
limit of f and the value of f at
each point of the function’s
domain.
Points at which f is discontinuous:
At x = 1,
DNE
At x = 2,
but
At c < 0, c > 4,
these points are not in the domain of f

5. Definition: Continuity at a Point
Interior Point: A function is continuous at
an interior point c of its domain if
Exterior: A function is continuous at a
left endpoint a or is continuous at a right endpoint
b of its domain if or ,
respectively.

6. Types of Discontinuity
Graph
Removable Discontinuity – The
function can be redefined at a single
point in order to “remove” the
discontinuity (the graph has a “hole” in it).
(0,1)
Removable discontinuity at x = 0

7. Types of Discontinuity
Graph
Jump Discontinuity – The one-sided
limits of the function at the given point
exist, but have different values.
(0,1)
Jump discontinuity at x = 0

8. Types of Discontinuity
Graph
Infinite Discontinuity – The function
approaches positive or negative infinity
as x approaches the given point.
Infinite discontinuity at x = 0

9. Types of Discontinuity
Graph
Oscillating Discontinuity – The
function oscillates with increasing
frequency as x approaches the given
point
Oscillating discontinuity at x = 0

10. Continuous Functions
A function is continuous on an interval if and only if it is
continuous at every point on the interval. A continuous
function is one that is continuous at every point of its domain.
Ex: Consider the reciprocal function
Does this function have any points of discontinuity?
Yes  The function has an infinite discontinuity at x = 0
Is this a continuous function?
Yes  The only point of discontinuity (at x = 0) is not in
the domain of the function, so the function is continuous
on its domain!!!

11. Theorem: Properties of Continuous Functions
If the functions f and g are continuous at x = c, then the
following combinations are continuous at x = c.
1. Sums:
2. Differences:
3. Products:
4. Constant Multiples:
for any number k
5. Quotients:
provided
Theorem: Composite of Continuous Functions
If f is continuous at c and g is continuous at f (c), then the
composite g f is continuous at c.

12. Guided Practice
For the following function, (a) find each point of discontinuity,
(b) Which of the discontinuities are removable? Not
removable? Give reasons for your answers.
(a) Point of discontinuity:
(b) Removable  reassign:
The graph?