向量真题口算技巧

=2[√3sinxcosx+cos？x]-1

=(√3)sin2x+[1+cos2x]-1

= 2[(√3/2)sin2x+(1/2)cos2x]

= 2[sin 2 xcos(π/6)+cos 2 xsin(π/6)]

=2sin(2x+π/6)

那么:f(x)=1就是2sin (2x+π/6) = 1。

sin(2x+π/6)=1/2

因为x∈[π/6，π/2]，那么2x+π/6 ∈ [π/2，7π/6]，那么:2x+π/6 = 5π/6，所以x=π/3。