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Discover Properties of Logarithms

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Today you are going to discover:

2 Patterns of Logs

4 Properties of Logs

1 Formula that will help you evaluate Logs in the calculator!

Pattern #1

Question 1
1.

Question 2
2.

Question 3
3.

Question 4
4.

Question 5
5.

Question 6
6.

Pattern #2

Question 7
7.

Question 8
8.

Question 9
9.

Question 10
10.

Question 11
11.

Inverse Property

Question 12
12.

What is the value of x?

Question 13
13.

Question 14
14.

Question 15
15.

Question 16
16.

Question 17
17.

This one is tricky! It's actually in Exponent form right now, so let's change it into Log form so we can figure out the answer:

What is the answer?

Question 18
18.

Notice a pattern from the previous example so you don't need to write out log form every time.

Question 19
19.

Question 20
20.

Question 21
21.

Same property, but now back to Log form again!

Question 22
22.

Here's a visual of what's happening in the inverse property:

Product Property

The product property is used to expand and condense logarithms.
Question 23
23.
Use your calculator to evaluate the following. Round all answers to the nearest tenth.

log(16)=_______
log(8â‹…2)=_______
log(8)+log(2)=_______

Therefore, we can expand log(8â‹…2) to log(8)+log(2) without changing the value of the logarithm.

Expand log(6â‹…3)=_______ <- type out the logs, not a decimal
Expand log(4â‹…x)=_______ <- type out the logs, not a decimal
Question 24
24.

Expand log(15)
*Hint: Any factors of 15 should work.

When expanding or condensing, always keep the base the same. For example:
Question 25
25.

Condense into one logarithm.
*Hint: your answer should only have one number inside the log

Question 26
26.

Expand into 3 separate logs.

Question 27
27.

Condense into one logarithm.

Question 28
28.

Condense into a single logarithm and evaluate.
Hint: your answer should be one number.

Question 29
29.

Quotient Property

The quotient property is also used to expand and condense logarithms.
Question 30
30.
Use your calculator to evaluate the following. Round all answers to the nearest tenth.

log(16)=_______
log(32\div 2)=_______
log(32)-log(2)=_______

Therefore, we can expand log(32/2) to log(32)-log(2) without changing the value of the logarithm.

Expand log(6\div3)=_______ <- write out two logs, not a decimal
Expand log(4/x)=_______ <- write out two logs, not a decimal
Question 31
31.

Expand into two logarithms.

Question 32
32.

Condense into one logarithm.

Question 33
33.

Can you apply the product AND quotient properties in the same problem??


Question 34
34.

Expand into 3 logarithms.
Remember to keep the base 11 on all of the logs in your answer!

Question 35
35.

Condense into one logarithm.

Question 36
36.

Condense into one logarithm and evaluate.
Your answer should be one number.

Question 37
37.

Condense into one logarithm and evaluate.
Your answer should be one number.

Power Property

Question 38
38.
Use your calculator to evaluate the following. Round all answers to the nearest tenth.

log(25)=_______
log(5^2)=_______
2\cdot log(5)=_______

Therefore, when taking the log of a power, we can bring the exponent down infront of the log without changing the value of the logarithm:

Use the power property to expand log(6^3)=_______
Use the power property to expand log(7^x)= _______
Question 39
39.

Use the power property to expand the logarithm.

Question 40
40.

Use the power property to expand the logarithm.

Question 41
41.

Use the power property to condense the logarithm.

Question 42
42.

Can you apply the product AND quotient AND power properties in the same problem??

Example for "expand"

Question 43
43.

Expand.

Question 44
44.

Expand.

Question 45
45.

Condense into a single logarithm.

Question 46
46.

Condense into a single logarithm and evaluate.
*Your answer should be one number.

Question 47
47.

Condense into a single logarithm and evaluate.

*Your answer should be one number.

Question 48
48.

Condense into a single logarithm and evaluate.
*Your answer should be one number.

Change of Base Formula

This formula allows us to evaluate logs in the calculator using the LOG button.
Question 49
49.
Use your calculator to evaluate the following. Round all answers to the nearest tenth.
\log _{10}\left(40\right)=_______

\frac{\log \left(40\right)}{\log \left(10\right)}=_______

Therefore, when evaluating a log, we can divide the log of the inside number by the log of the base without changing the value of the logarithm. This will work for any base, but it makes sense for us to use \log _{10} or ln since that is on our calculators.

Change of Base Examples:





Use the change of base formula to evaluate in the calculator:
\log _{4}\left(85\right)=_______
\log _{16}\left(64\right)= _______
Question 50
50.

What is the Change of Base Formula?

Copy your answer on your paper for Change of Base Formula.

What's the pattern?
Select TWO: the correct "math" and "words" that describe the pattern.

Copy your answers on your paper for Pattern #1.
When the base of the log matches the number inside the log, the log equals 0.
When the base of the log matches the number inside the log, the log equals 1.
When the base of the log matching the number inside the log, the log equals the base.
What's the pattern?
Select TWO: the correct "math" and "words" that describe the pattern.

Copy your answers on your paper for Pattern #2.
The log of 1 will always equal the base.
The log of 1 will always equal 0.
The log of 1 will always equals 1.
What is the Inverse Property?
Select THREE: two correct "math" examples and one "words" example that describe the property.

Copy your answers on your paper for Inverse Property.
If the base of the log matches the base of the exponent, they cancel out, and the answer is what's left.
If the base of the log matches the base of the exponent, the answer will always equal the base.
If the base of the log matches the base of the exponent, the answer will always equal 1.
What is the Product Property?
Select TWO: the correct "math" and correct "words" that describe the property.

Copy your answers on your paper for Product Property.
The log of a product equals the sum of the logs of its factors. (multiply inside = add outside)
The log of a product equals the difference of the logs of its factors. (multiply inside = subtract outside)
The log of a sum equals the product of the logs of its factors. (add inside = multiply outside)
What is the Quotient Property?
Select TWO: the correct "math" and correct "words" that describe the property.

Copy your answers on your paper for Quotient Property.
The log of a quotient equals the sum of the logs of its divisors. (divide inside = add outside)
The log of a difference equals the quotient of the logs of its factors. (subtract inside = divide outside)
The log of a quotient equals the difference of the logs of its divisors. (divide inside = subtract outside)
What is the Power Property?
Select TWO: the correct "math" and correct "words" that describe the property.

Copy your answers on your paper for Power Property.
The log of a power equals the product of the log and exponent.
The log of a power equals the product of the log and the power.
The log of a power equals the sum of the log and exponent.
The log of a power cancels out the base and equals the exponent.