SOLUTION: Find the exact value of the expression, if it is defined. (If it is not defined, enter NONE.) cos^-1(cos(-pi/2)) Now, I keep getting 1.570796327 as the answer but it keeps sa

Question 871827: Find the exact value of the expression, if it is defined. (If it is not defined, enter NONE.)
cos^-1(cos(-pi/2))
Now, I keep getting 1.570796327 as the answer but it keeps saying it is incorrect. I also tried pi/2 which is the same thing but it also says it is incorrect. Just a little confused.
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
Find the exact value of the expression, if it is defined. (If it is not defined, enter NONE.)
cos^-1(cos(-pi/2))
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Ans: -pi/2
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Cheers,
Stan H.
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