In order to do this, simply find the option in the range where only the cos is +ve. This occurs in the range 270∘≤x≤360∘270^{\circ} \leq x \leq 360^{\circ}270∘≤x≤360∘.
Check: sin 300=−sin 60=−32\sin \; 300 = - \sin \; 60 = \frac{-\sqrt{3}}{2}sin300=−sin60=2−3
cos300=cos60= 12\cos 300 = \cos 60 = \; \frac{1}{2}cos300=cos60=21
