∵曲线f(x)= sinx sinx+cosx ? 1 2 ,∴f′(x)= cosx(sinx+cosx)?sinx(cosx?sinx) (sinx+cosx)2 = 1 1+sin2x ,∴当x= π 4 时,f′( π 4 )= 1 1+sin(2× π 4 ) = 1 2 ,又切点M坐标为( π 4 ,0),∴所求切线方程为x?2y? π 4 =0,故答案为:x?2y? π 4 =0,