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How to Put Logarithms Into A Calculator Ti 84

Reviewed by Calculator Editorial Team

Calculating logarithms on your TI-84 calculator is straightforward once you understand the basic steps. This guide will walk you through entering and solving logarithmic expressions using your TI-84, including common logarithm (base 10) and natural logarithm (base e) calculations.

Basic Logarithms

To calculate a common logarithm (base 10), follow these steps:

  1. Press the 2ND key.
  2. Press the LOG key (this will display "log" on the screen).
  3. Enter the number you want to find the logarithm of.
  4. Press the ENTER key to see the result.

The formula for common logarithm is: log10(x)

For example, to calculate log10(100):

  1. Press 2ND then LOG.
  2. Enter 100.
  3. Press ENTER to get 2.

Natural Logarithms

For natural logarithms (base e), use these steps:

  1. Press the LN key.
  2. Enter the number you want to find the natural logarithm of.
  3. Press the ENTER key to see the result.

The formula for natural logarithm is: ln(x)

For example, to calculate ln(e):

  1. Press LN.
  2. Enter 2.71828 (the value of e).
  3. Press ENTER to get approximately 1.

Logarithmic Equations

To solve logarithmic equations, follow these steps:

  1. Enter the equation in the form log10(x) = y or ln(x) = y.
  2. For common logarithms: Press 2ND then LOG, then enter the right side of the equation.
  3. For natural logarithms: Press LN, then enter the right side of the equation.
  4. Press the = key to solve for x.

To solve log10(x) = 2, you would calculate 102 = 100.

For example, to solve log10(x) = 3:

  1. Press 2ND then LOG.
  2. Enter 3.
  3. Press = to get x = 1000.

Common Mistakes

When working with logarithms on your TI-84, be aware of these common errors:

  • Using the wrong logarithm function (LOG for base 10, LN for natural log).
  • Forgetting to press ENTER after entering the number.
  • Confusing the base of the logarithm with the result.
  • Entering negative numbers when the logarithm is only defined for positive real numbers.

Remember that logarithms are only defined for positive real numbers. Attempting to calculate log10(-5) or ln(0) will result in an error on your calculator.

Frequently Asked Questions

Can I calculate logarithms with different bases on my TI-84?

Yes, you can calculate logarithms with different bases using the change of base formula: logb(x) = ln(x)/ln(b). You'll need to use the LN function for both the numerator and denominator.

How do I clear the logarithm function from my calculator?

Press the 2ND key, then the LOG key again to clear the logarithm function from the display.

What if my TI-84 shows an error when calculating logarithms?

Common errors include entering a negative number or zero. Make sure your input is a positive real number. If you're still having issues, check that you're using the correct logarithm function (LOG for base 10, LN for natural log).