Question 1144204
<br>
{{{sin(60) = sqrt(3)/2}}}<br>
A 60 degree reference angle in any quadrant will give you a sine value of {{{sqrt(3)/2}}} or {{{-sqrt(3)/2}}}.<br>
Sine is positive in quadrants I and II; so the smallest positive angle with a sine of {{{-sqrt(3)/2}}} will be in quadrant III.<br>
A 60 degree reference angle in quadrant III is 240 degrees.<br>
Since the answer choices are in radians, 240 degrees is 4π/3 radians.<br>
So answer b.<br>
Note for your answer a the reference angle is the correct 60 degrees or π/3 radians; but it is in quadrant II, where the sine value is positive, not negative.