Question 1093717
<br>The general form for a sine of cosine function is<br>
{{{a*sin(b(x-c))+d}}}<br>
In that form...
a is the amplitude;
b determines the period;   (the period is (2pi)/b)
c is the horizontal shift; and
d is the vertical shift.<br>
With your function, the period would be
{{{2pi/(pi/9) = 18}}}<br>
That is not any of the given answer choices....<br>
Since all of the answer choices involve the number 11 or 22, I suspect the given function is supposed to have b equal to (pi/11) instead of (pi/9).  In that case, the period would be
{{{2pi/(pi/11) = 22}}}<br>
answer choice C