The arctan function represent the inverse of the tangent function. If the tangent of a number is a second number, the arctan of the second number is the first number. The function is useful when solving trigonometric problems. If you know the two shorter lengths in a right-angled triangle, the arctan of the ratio between them equals the angle between one of them and the hypotenuse.

Step 1

Search your calculator for the arctan button, which will be marked as either “arctan,” “atan” or “tan-1.” If the calculator has an arctan button, press it and skip to Step 3. If it doesn’t, continue to Step 2.

Step 2

Press the calculator’s “shift,” “2nd” or “function” key, and then press the “tan” key.

Step 3

Type the number whose arctan you want to find. For this example, type in the number “0.577.”

Step 4

Press the “=” button. The number’s arctan will appear. The arctan of 0.577, for instance, is approximately 30.