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## PowerPoint Slideshow about 'Continuity Curves without gaps?' - hal

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Continuity

DefinitionA function f is continuous at a number aif

lim f(x) = f(a).

x -> a

1. f (a) is defined.

2. lim f(x) exists.

x -> a

3.lim f(x) = f(a).

x -> a

If f is not continuous at a , we say f is discontinuous at a, or f has a discontinuity at a .

Example Where is the function

f(x)=(x 2 – x – 2)/(x – 2) discontinuous?

DefinitionA function f is continuous from the right at a number a if

lim f(x) = f(a),

and f is continuous from the left a if

lim f(x) = f(a).

x -> a +

x -> a-

DefinitionA function f is continuous on an interval if it is continuous at every number in the interval.

At an endpoint of the interval we understand continuous to mean continuous from the right or continuous from the left.

Example Use the definition of continuity and the properties of limits to show that the function

f (x) = x 16 –x2is continuous on the interval [-4, 4].

_____

Theorem If f and g are continuous at a and c is a constant, then the following functions are also continuous at a:

1. f + g 2. f – g 3. c f

4. f g 5. ( f / g) if g(a) is not

equal to 0.

Theorem

- Polynomials are continuous everywhere; that is continuous on R = (-, ).
- Any rational function is continuous wherever it is defined; that is, it is continuous on its domain.

TheoremThe following types of functions are continuous at every number in their domains:

-polynomials -rational functions -root functions -exponential functions -trigonometricfunctions -inverse trigonometric functions -logarithmic functions.

Theorem If f is continuous at b and lim g(x) = b, then, lim f(g(x)) = f(b).

In other words,

lim f(g(x)) = f(lim g(x)).

x -> a

x -> a

x -> a

x -> a

Theorem If g is continuous at a and f is continuous at g(a), then

(f o g)(x) = f(g(x)) is continuous at a.

The Intermediate Value Theorem

Suppose that f is continuous on the closed interval [a, b] and let N be any number strictly between f (a) and f (b). Then there exists a number c in (a,b) such that f (c)=N .

Example Use the Intermediate Value Theorem to show that there is a root of the given equation in the specified interval.

ln x = e –x , (1,2).

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