Question 1153893
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I came to make two notices.



First, "phi" in your condition is not "phi" ---- actually, it is "pi", instead. // Learn how to write it correctly (!)


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    By the way, yesterday was National  (and International)  "pi-day" (!)
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Second, I want to correct the answer by other tutor:


<pre>
    if  0 <= x < 2*pi, then the solutions are these four values  x = {{{pi/3}}}, {{{5pi/6}}}, {{{4pi/3}}} and {{{11pi/6}}}.
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