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Mathematics for Technology II (Math 2131)

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Study Force Academy
Durham College, Mathematics
Free
  • 36 lessons
  • 0 quizzes
  • 14 week duration

Converting between exponential and logarithmic form

None of the math you’ve learned so far in this course and in the previous has gone so far to help us solve for ‘x’ in a situation depicted below. Notice that the variable is located in the exponent part of the equation:

2x=8

Through visual inspection, however, ‘x’ is equal to 3, but your math intuition will likely begin to fail once you start seeing decimals or larger numbers. Therefore, we need to rely on a method that more sustainable or something that will not fail. So for this and similar problems, we use logarithms. By making the base of the log 2, then finding the log of 8, we get x = 3:

log28=xx=3
  • This is read: “log base 2 of 8 equals x”. The main learning goal for this lesson is being able to convert from one form to another.

These two statements are completely equivalent, but what just happened? The base ‘2’ became the logarithm base, while the power ‘x’ became the answer. This relationship is summarized below, and you’ll need to know this for future reference.

⚠️ Before we continue, that as a reminder you were expected to have an Casio fx-991ES Plus calculator for this course. This calculator, unlike most scientific calculators, has a feature that enables its users to customize the base of a logarithm. Rather, the general function found on most scientific calculators only allows you to find the answer when the base is 10. Therefore, for those that don’t have this calculator, these next few examples cannot be evaluated electronically, but you will be expected to know how to convert from exponential to logarithmic form. Instead, you’ll need to know the properties of logarithms that are being introduced next section to solve for the variable found in the exponent.

Convert the following equations to logarithmic form:

53=125 100=102

Solutions:

log5125=3 log10100=2

By convention, when the base of the log is 10, we don’t write it in as it’s assumed:

 log100=2

Convert the following equations to exponential form:

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