E. Using the Tangent Ratio with a Calculator

Until now, you have been referencing the tangent table to determine an angle measure from a tangent ratio or the tangent ratio from an angle measure. The table you’ve been using provides the approximated information for some angles, but not for all possible angles. Fortunately, most scientific and most graphing calculators are able to provide this information for all angles and ratios.

To determine the tangent ratio of an angle, use the “tan” function.

Example 1

Determine the value of tan 42.7°.

Use the tan function on your calculator.

  • In some calculators you will enter: tan 42.7 enter or = .

  • In some calculators you will enter: 42.7 tan = .

If you have entered it correctly into your calculator, you should get an answer of 0.92277….

tan 42.7° = 0.92277...

It may help to think of this tan 42.7° value as part of the table from earlier in the lesson.

35° 0.70 0.70
40° 0.84 0.84
42.7° 0.92277… 0.92277…
45° 1 1
50° 1.19 1.19

IMPORTANT
All angles in this course are measured in degrees, so you will need to make sure your calculator is in degree mode. Many calculators show a “D” or “deg” when in degree mode.

  • Try to determine the value of tan 42.7°. If you get an answer of 0.92277…, you are in the correct mode.

  • If you get an answer of –3.369… or 0.796…, you are in the wrong mode. If you receive any other value, you may be entering the information incorrectly.

If you are unsure how to change the mode of your calculator, refer to the calculator’s manual, or contact your teacher.