On some calculators the arccos button may be labelled acos, or sometimes cos So the inverse of cos is arccos etc. Use arccos when you know the cosine of an angle and want to know the actual angle. See also Inverse functions - trigonometry. In the above figure, click on 'reset'. We know the side lengths but need to find the measure of angle C. We know that so we need to know the angle whose cosine is 0. Recall that we can apply trig functions to any angle , including large and negative angles.
But when we consider the inverse function we run into a problem, because there are an infinite number of angles that have the same cosine. For more on this see Inverse trigonometric functions. I know this formula and have it written down.
However I've left my calculator and I'm having to use Google:. Wolfram Alpha gives about My calculator gives Also between the numbers in the denominator I get spaces instead of asterisks, so maybe it is not multiplying. Some people distinguish between the inverse cosine function which has the range restricted so there is only one value and arccos not having the range restricted so it is multivalued, but that doesn't seem to be your problem.
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Add a comment. Active Oldest Votes. Ross Millikan Ross Millikan k 26 26 gold badges silver badges bronze badges. When you choose a, b, and c that designates which angle you are solving for. In your previous comment you are solving for the angle across from side a.
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