(x)=a[cos^2(x) sinxcosx] b =a[(1 cos2x)/2 (1/2)(2sinxcosx)] b =a[(1/2)sin2x (1/2)cos2x 1/2] b =a[(1/2)(sin2x cos2x)] (a 2b)/2 =(√2a/2)sin(2x π/4) (a 2b)/2 则：(1) 由于：a>0 则：当f(x)单调递增时,2kπ...