Exponential Modeling and Logarithms

Lesson 10

Math

Unit 5

11th Grade

Lesson 10 of 16

Objective


Evaluate common and natural logs using tables, graphs, and calculators.

Common Core Standards


Core Standards

  • F.BF.B.4.C — Read values of an inverse function from a graph or a table, given that the function has an inverse.
  • F.LE.A.4 — For exponential models, express as a logarithm the solution to abct = d where a, c, and d are numbers and the base b is 2, 10, or e; evaluate the logarithm using technology.

Criteria for Success


  1. Describe the common log as the inverse of an exponent with a base of 10.
  2. Describe the natural log as the inverse of an exponent with a base of $$e$$.
  3. Identify key points of common and natural logs using a table of values.
  4. Evaluate common and natural logs without a calculator when possible.
  5. Use a calculator to evaluate common and natural logs and connect these values to tables and graphs.
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Anchor Problems

25-30 minutes


Problem 1

Given: $${f(x)=e^x}$$ and $${g(x)=10^x}$$

Use your calculator to write a table of values for $${f^{-1}(x)}$$ and $${g^{-1}(x)}$$.

Match the equivalent equations with the tables of values above.

Which graph below represents $${\mathrm{log}_{10}x}$$ and which represents $${\mathrm{log}_ex}$$?

Guiding Questions

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Problem 2

The “Common Log” is a log with a base of $${10}$$. This is written as $${\mathrm{log}(x)}$$.
The “Natural Log” is a log with a base of $$e$$. This is written as $${\mathrm{ln}(x)}$$.

Write each of the following exponential equations as either a common log or the natural log. 

$${10}^x=y$$

$$e^x=y$$

Guiding Questions

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Target Task

5-10 minutes


Joseph evaluated $${\mathrm{log}_232}$$ in his calculator and got $${1.505}$$. Why does his answer not make sense? How did he “plug in” the value in the calculator? 

Next

Understand and apply the change of base property to evaluate logarithms.

Lesson 11
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Lesson Map

A7CB09C2-D12F-4F55-80DB-37298FF0A765

Topic A: Modeling with and Interpreting Exponential Functions

Topic B: Definition and Meaning of Logarithms

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