2.9

Logarithmic Expressions

about 25 min · 6 short parts · stop after any part
A log is just a question: *"what power do I need?"*
By the end you can answer it in your head, on a calculator, and read log-scale graphs (earthquakes, sound, YouTube views).

The path

  1. 1
    Exponents, fast refresh
    You can read 232^3, 2−32^{-3} and 91/29^{1/2}.
  2. 2
    What a log asks
    You can read log⁡28\log_2 8 as a question and answer it.
  3. 3
    Switching forms
    You can rewrite a log as an exponent and back.
  4. 4
    Logs without a calculator
    You can solve log⁡2781\log_{27} 81 with same-base powers.
  5. 5
    Logs with a calculator
    You can find log⁡425\log_4 25 to 3 decimals.
  6. 6
    Log scales
    You can place and compare values on a log scale.