sin(-7/6π)=sin(2π-7π/6)=sin5π/6=1/2cos(15/4π)=cos(4π-π/4)=sin(-π/4)=cos(v/4)=√2/2tan(-8/3π)=tan(-3π+π/3)=tan(π/3)=√3tan(33/4π)=tan(8π+π/4)=tan(π/4)=1