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Limits cont. Evaluating them- Numerically, Anallyitically and Graphically. 1.3 Properties of Limits :. Properties :. Scalar multiple Sum or difference Product Quotient Power. Scalar multiple :. - PowerPoint PPT Presentation
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LIMITS CONT.Evaluating them-
Numerically, Anallyitically and Graphically
1.3 PROPERTIES OF LIMITS:
limx cb b
1lim5 5x
limx cx c
lim n n
x cx c
2lim 2xx
3 3
4lim 4xx
64
PROPERTIES: Scalar multiple
Sum or difference
Product
Quotient
Power
let b and c be real numbers, let n be a positive integer, and let f and g be functions with the following limits:
let b = 2, c = 5, f(x) = x and g(x)=x2
SCALAR MULTIPLE :
limx cf x L
lim
x cg x M
limx cbf x bL
5lim 2x
x
2 5 10
let b and c be real numbers, let n be a positive integer, and let f and g be functions with the following limits:
let b = 2, c = 5, f(x) = x and g(x)=x2
SUM OR DIFFERENCE:
limx cf x L
lim
x cg x M
lim limx c x cf x g x L M
2
5 5lim limx xx x
5 25 30
let b and c be real numbers, let n be a positive integer, and let f and g be functions with the following limits:
let b = 2, c = 5, f(x) = x and g(x)=x2
PRODUCT:
limx cf x L
lim
x cg x M
lim limx c x cf x g x L M
2
5 5lim limx xx x
5 25 125
let b and c be real numbers, let n be a positive integer, and let f and g be functions with the following limits:
let b = 2, c = 5, f(x) = x and g(x)=x2
QUOTIENT:
limx cf x L
lim
x cg x M
limx c
f x Lg x M
2limx c
xx
5 125 5
( ),M 0g x
let b and c be real numbers, let n be a positive integer, and let f and g be functions with the following limits:
let b = 2, c = 5, f(x) = x and g(x)=x2
POWER:
limx cf x L
lim
x cg x M
limn n
x cf x L
3
5limx
x
35 125
Functions can all be combined to form more complex functions:
We can also look at this another way:
Sometimes this makes it easier to calculate… we will deal with this more in the future.
COMPOSITION OF FUNCTIONS:
2 4 f x x g x x
0
lim ?xg f x
2
0lim 4 0 4 2x
x
2
0lim 4 0 4 2x
x
TRIGONOMETRIC LIMITS: Let c be a real number in the domain of
the given trigonometric function:
This works this way for all of the trig functions.
limsin sinx c
x c
TRIGONOMETRIC LIMITS:
0lim tanx
x
tan 0 0
lim cosxx x
cos
2
4
lim sinx
x
2
4
lim sinx
x
2
4
lim sinx
x
2
sin4
22 1
2 2
FINDING LIMITS:DIVIDING OUT TECHNIQUEConsider
Direct substitution yields an indeterminate form.Graph it. What does the function approach as x gets closer to 2?What about a table? What does it look like it is approaching?Can we do algebra? (see next slide for steps)
What answer does that give us?
3
2
8lim2x
xx
USE ALGEBRA: Find: Use :
So, = = 12
SOLVING LIMITS: direct substitution.
Simplify using algebra and then try direct substitution again.
Use a graph or a table to reinforce your conclusion or to evaluate the limit if you are allowed to use technology.
SQUEEZE THEOREM: Not necessary for AP to be added later
DEFINITION Formal Definition:
Epsilon-deltaThis formal definition is rather intimidating when you first look at it, but when broken down it makes sense.
ONE-SIDED LIMITS: Lets look at x3. The limit from the left = ?
1 The limit from the right = ?
4 Are they equal?
NO Does the limit exist?
NO!!!
ONE-SIDED LIMITS:• As we approach 3 from the left, we are approaching
what value for the function? • What about from the right?
EVALUATING ONE-SIDED LIMITS:Consider the following problem:
When we do direct substitution, what do we get?
We can do some algebra: First factor…
Now calculate the limit:
2
1
2 3lim1x
x xx
2 3 12 3 31 1
x xx x xx x
22
1
1 2 1 32 3 0lim1 1 1 0x
x xx
2
1 1
2 3lim lim 3 ???1x x
x x xx
ANOTHER APPROACH:
x -1 -.999 -.99 -.9f(x) ?
What does it appear to be heading towards?
Did we get the same value as the previous technique?
2
1
2 3lim1x
x xx
APPLICATIONS Continuity
This is covered in the next section Asymptotes
This is used in Curve Sketching (without a calculator!)
HOMEWORK: Pg 67 #6-40E