sin(105-a)+cos(375-a)
=sin[180-(105-a)]+cos(360+15-a)
=sin(a+75)+cos(15-a)
=sin(a+75)+sin(90-15+a)
=2sin(a+75)
-180-105所以sin(a+75)<0
cos(a+75)=1/3
所以原式=2sin(a+75)=-2√[1-(1/3)^2]=-4√2/3