括号中是sinx+cosx吗?f(x)=2asinxcosx-√2a(sinx=cosx)+a+b=[(sinx+cosx)²-1]a-a√2(sinx+cosx)+a+b 因为x∈[0,π/2] 故x+π/4∈[π/4,3π/4], sinx+cosx=√2sin(x+π/4) 得1≤sinx+cosx≤√2 设sinx+cosx=y 则...