sin(-9/4π) + cos(-9/4π) + tan(-9/4π) =sin(-9/4π+4π) + cos(-9/4π+4π) + tan(-9/4π+3π)=sin(7/4π) + cos(7/4π) + tan(3/4π)=sin(1/4π)-cos(1/4π)+tan(3/4π)=根号2/2-根号2/2-1=-1