Learning Resources

Focus B: Other Trigonometric Functions & Investigation 5: Other Trigonometric Functions

Your calculator does not have special keys for the reciprocal functions. The fact is, calculators do not need special keys to work with the reciprocal trigonometric functions. The keys for the primary trigonometric functions will suffice.

Suppose you wanted to evaluate csc 21°. You need to determine how you can arrive at the solution using the keys for the primary trigonometric functions. Since cosecant is the reciprocal of sine, you can write . Thus you can simply enter "1 divided by sin 21" into your calculator. Be sure your calculator is in degree mode!. Alternatively, you can enter sin (21)and then press x^-1, the reciprocal key. Either way, you are taking the reciprocal of the sine of 21°. You should obtain an answer of 2.7904.

To be sure you understand the process, verify that you can obtain the following solutions on your calculator.

csc55° = 1.2208          sec76° = 4.1336          cot109°= -0.3443