Question 1197163
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For the inverse cosine function, the input is a real number between -1 and +1, and the output value is in a range which is the interval closest to 0 in which cos(x) takes on all it values.<br>
cos(x) takes on all its values on [0,pi), so the output of the inverse cosine function is on that interval.  Note cos(x) also takes on all its value on [-pi,0); but the convention is to use the interval where the numbers are positive.<br>
cos(x) has a period of 2pi, so cos^(-1)(cos(x)) returns a value equal to x, plus or minus the multiple of 2pi that makes the output value between 0 and pi.<br>
Since in this problem the input value x is between -pi and 0, the output value needs to be x+2pi.<br>
ANSWER: C<br>