check your Unit Circle for all angles on that range that have a cosine of 1/2 then divide that by 4... for example hmmmm say [tex]\bf \frac{\pi }{3}[/tex] is one, thus x = [tex]\bf \cfrac{\frac{\pi }{3}}{4}\implies \cfrac{\pi }{3}\cdot \cfrac{1}{4}\implies \cfrac{\pi }{12}[/tex]