10-4 Common Logarithms Objective: To identify the characteristic and the mantissa of a logarithm. To find common logarithms and antilogarithms.

Vocabulary Mantissa – The decimal portion of a logarithm. Characteristic – The integer portion of a logarithm. Antilogarithm – When you are given the logarithm of a number and asked to find the number, you are finding the antilogarithm.

Example 1 If log 1.2 ≈ .0792, find each of the following. log 120

Example 2 log 120 ≈ 2.0792 Characteristic = 2 Mantissa = .0792

Example 3 log .0007 ≈ -3.1549 Characteristic = -4 (use the integer to the left) Mantissa = .8451 (add the opposite of the characteristic)

Example 4 Use a scientific calculator to find the antilogarithm of 3.073. log x = 3.073

Assignment 10-4 pg 620 #12-24 even