$\eqalign{
& \sin \left( {\frac{{7\pi }}{3}} \right) = \sin \left( {2\pi + \frac{\pi }{3}} \right) = \sin \left( {\frac{\pi }{3}} \right) = \frac{{\sqrt 3 }}{2} \cr
& \cos \left( {\frac{{5\pi }}{4}} \right) = \cos \left( {\pi + \frac{\pi }{4}} \right) = - \cos \left( {\frac{\pi }{4}} \right) = - \frac{{\sqrt 2 }}{2} \cr
& tg\left( { - \frac{\pi }{3}} \right) = - tg\left( {\frac{\pi }{3}} \right) = - \sqrt 3 \cr
& \cos \left( {\frac{{7\pi }}{6}} \right) = \cos \left( {\pi + \frac{\pi }{6}} \right) = - \cos \left( {\frac{\pi }{6}} \right) = - \frac{{\sqrt 3 }}{2} \cr
& = - \frac{{\sqrt 6 }}{4} = \frac{3}{2} \cr} $