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Properties of the Natural Log Function
• If a and b are positive numbers and n is rational, then the following properties are true:
ln(1) 0
ln( ) ln lnab a b
ln( ) lnna n a
ln ln lna
a bb
The Algebra of Logarithmic Expressions
10ln ln10 ln 9
9
1/ 2 1ln 3 2 ln 3 2 ln 3 2
2x x x
6ln ln 6 ln 5
5
xx
22
3 2
3ln
1
x
x x
The Derivative of the Natural Logarithmic Function
Let u be a differentiable function of x
1ln , 0
dx x
dx x
ln , 0d u
u udu u
Differentiation of Logarithmic Functions
ln APPLY PRODUCT RULE!!!!!!!!!!dx x
dx
11 ln x x
x
ln 1x
ln ln lnd d dx x x x x x
dx dx dx
Differentiation of Logarithmic Functions
3ln CHAIN RULE!!!
dx
dx
23 ln ln
dx xdx
23 ln x
x
2 13 ln x
x
Logarithmic Properties as Aids to Differentiation
• Differentiate:
ln 1f x x
1/2 1ln 1 ln 1
2f x x x
11 1
2 1 2 1
xf x
x x
Logarithmic Differentiation
• Differentiate:
This can get messy with the quotient or product and chain rules. So we will use ln rules to help simplify this and apply implicit differentiation and then we solve for y’…
2
2
2
1
xf x
x
Derivative Involving Absolute Value
• Recall that the ln function is undefined for negative numbers, so we often see expressions of the form ln|u|. So the following theorem states that we can differentiate functions of the form y= ln|u| as if the absolute value symbol is not even there.
• If u is a differentiable function such that u≠0 then:
lnd u
udu u
Derivative Involving Absolute Value
• Differentiate: ln cosf x x
ln cosd u
xdx u
cos , sinu
u x u xu
sin
cos
u x
u x
Finding Relative Extrema
• Locate the relative extrema of • Differentiate:
• Set = 0 to find critical points=02x+2=0X=-1, Plug back into original to find yy=ln(1-2+3)=ln2 So, relative extrema is at (-1, ln2)
General Power Rule for Integration
• Recall that it has an important disclaimer- it doesn’t apply when n = -1. So we can not integrate functions such as f(x)=1/x.
• So we use the Second FTC to DEFINE such a function.
Using the Log Rule for Integration
2dxx
1Factor out the constant:2
This gives us a form we recognize and can easily integrate.
dxx
2ln x c
2Use rules to clean things up:ln x c
Using the Log Rule with a Change of Variables
( 14 𝑥−1 )𝑑𝑥 Let u=4x-1, so du=4dx
and dx=
1ln
4u c
1ln 4 1
4x c
Finding Area with the Log Rule
• Find the area of the region bounded by the graph of y, the x-axis and the line x=3.
3 3
20 0Set up your integral: ( )
1
xy x dx dx
x
We have an integral in the form
u
u
2 1 so 2Let u x u xdx
2
1 1 1 12
2 1 2xdx du
x u
3
2
0
1 1ln ln 1
2 2u x
2 21 1 1 1 1ln 3 1 ln 0 1 ln10 ln 1 ln10 ln 10
2 2 2 2 2
2 1
xy x
x
Recognizing Quotient Forms of the Log Rule
23 3
3
3 1ln
xdx u x x x x c
x x
2sectan ln tan
tan
xdx u x x c
x
1/31 1 3 13 2 ln 3 2 ln 3 2
3 2 3 3 2 3dx u x dx x c x c
x x
DefinitionThe natural logarithmic function is defined
by
The domain of the natural logarithmic function is the set of all positive real numbers
1
1ln , 0
xx dt x
t
u-Substitution and the Log Rule1
_ _ln
dya differential equation
dx x x
1_ _ :
lnIntegrate both sides y dx
x x
1lnu x du dx
x
uduu
ln u c
ln ln x c
How you know it’s long Division
• If it is top heavy that means it is long division.o Example
3 2
2
4 4 96 100
25
x x x
x
Using Long Division Before Integrating
2
2
1
1
x xdx
x
22 2
2 2
11
1 1 11 1
rxx x x
dx x x xx x
21
1
xdx
x
2 1
xdx dx
x
21ln 1
2x x c
2: 1 0, ... _ _ _ _ _Note x x so no need for absolute value
Guidelines for integration
1. Learn a basic list of integration formulas. (including those given in this section, you now have 12 formulas: the Power Rule, the Log Rule, and ten trigonometric rules. By the end of section 5.7 , this list will have expanded to 20 basic rules)
2. Find an integration formula that resembles all or part of the integrand, and, by trial and error, find a choice of u that will make the integrand conform to the formula.
3. If you cannot find a u-substitution that works, try altering the integrand. You might try a trigonometric identity, multiplication and division by the same quantity, or addition and subtraction of the same quantity. Be creative.
4. If you have access to computer software that will find antiderivatives symbolically, use it.
Integrals of the Six Basic Trigonometric Functions
sin cosudu u c cos sinudu u c tan ln cosudu u c cot ln sinudu u c
sec ln sec tanudu u u c csc ln csc cotudu u u c