INVERSE TRIG FUNCTIONS Evaluating (Page 4 of 10)

Now we will use an inverse trigonometric function to find the measure of an angle whose tangent is -1. Simply evaluate arctan(-1).

 CLEAR key.

 2nd inverse tangent key. Negation key. 1 Right parenthesis key. ENTER key.

 Calculator screen image.

We find that a 45° angle measured clockwise has a tangent of -1.

It is important to be aware of the range for these three inverse functions. The arcsine will only return an angle between -90° and 90°(inclusive), the arccosine will return an angle between 0 and 180° (inclusive), and the arctangent will return an angle between -90° and 90°. That is why we obtained the result of -45° instead of 135°.
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