sinx+cosx = (根号2)sin(x+π/4) 值域[-根号2,根号2]sin^x-cosx+1 = 1-cos^x+1 = -(cosx+1/2)^+9/4值域[0,9/4]y = cosx/(2cosx+1) 所以cosx = y/(2y-1)在-1到1之间解得值域(-无穷,1/3]∪[1,+无穷)...