Evaluating Lograrithms

 The Problem Evaluate each logarithm. a). b). c). d).

The calculator can be used to evaluate each of these logarithms. Since the calculator directly evaluates only common logarithms (base 10) and natural logarithms (base e), the change of base formula is needed for parts a, b, and c of the problem above.

 Change of Base Formula:

Solution to part a:

a). Rewite . To enter this expression in the calculator, press ALPHA Y=. Select 1:n/d, the enter LOG 8), down arrow and LOG 2). Then press ENTER. See the results below.

Thus = 3

b). Rewrite . To enter this expression, press ALPHA Y=. Select 1:n/d, the press LOG and press ALPHA Y=. Select 1:n/d. Type 1, down arrow and 25 ) down arrow and type LOG 5). The press ENTER. See the results below.

Thus = -2.

c). Rewrite . To enter this expression press ALPHA Y=. Select 1:n/d, then press LOG 49), then down arrow and LOG 7). Then press ENTER. See the results below.

Thus = 2.

d). Since the base of this logarithm is e, enter the expression by pressing LN 2nd, then LN -7)). Then press ENTER.

Thus = -7.