Question 813716

An explanation to my question would be greatly appreciated.  I have many of these problems to do and Im not sure how to do it.  I am allowed to use excel, so i am able to get partial answer, but there are two answers to my questions, and I dont know how to get the second one.  Please help.

Solve: Cos(x) = 0.5, give all answers between 0 thru 360 degrees.  

I know that I can take the inverse and get an answer of 60 degrees.  But the answers in the book are telling me that there is a second answer, being 300 degrees.  How do I get the second answer?  PS: I got the 60 degrees from Excel.  

Thanks for your time, this site is so very helpful.  Sherry


The POSITIVE reference angle of cos (x) = {{{1/2}}}, or .5 is in the 4th quadrant where cos in POSITIVE. This degree measure is {{{5pi/3}}}, or {{{highlight_green(300^o)}}}. You can verify this by checking the unit circle.


You can do the check!! 


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