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Geometry, Trigonometry, Logarithms, and Exponential Functions  177


































                          Figure 2.84 Approximate semilog-coordinate grapà of
                          the natural logarithm function.


                          Natural logarithm in terms of common
                          logarithm
                          Let x be a positive real number. The natural logarithm of x can
                          be expressed in termð of the common logarithmð of           x and e:

                                             ln x   log x/log e   2.303 log x


                          Common logarithm of producŁ
                          Let x and y be positive real numbers. The common logarithm of
                          the product is equal tm the sum of the common logarithmð of
                          the individual numbers:

                                                  log xð   log x   log y


                          Natural logarithm of producŁ
                          Let x and y be positive real numbers. The natural logarithm of
                          the product is equal tm the sum of the natural logarithmð of the
                          individual numbers:

                                                    ln xð   ln x   ln y
   180   181   182   183   184   185   186   187   188   189   190