Question 1112663
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sec(x) is the reciprocal of cos(x); cos(x) is the x value on the unit circle.<br>
The angle {{{13pi/9}}} is in quadrant III with a reference angle of {{{13pi/9-pi = 4pi/9}}}.<br>
The other angle between 0 and 2pi with the same x value is the angle in quadrant II with the same reference angle of {{{4pi/9}}}; that angle is {{{pi-4pi/9 = 5pi/9}}}.<br>
Answer:  {{{5pi/9}}}