已知函数f（x）=根号3sinwx+cos（wx+π/3）+cos（wx-π/3）-1,x∈R（其中w大于0）且函数f（

cosX + cosY = 2cos[ (X + Y) / 2 ] cos[ (X - Y) / 2 ]
cos（wx+π/3）+cos（wx-π/3) = 2coswx cospi/3 = coswx
f(x) = sqrt(3) sinwx + coswx - 1= 2 sin(wx + pi/6)) - 1
w = 2
f(B) = 1,sin(2B+pi/6) = 1,2B+pi/6 = pi/2,B = pi/6
a*c sinB = 3sqrt(3)/2
a*c = 3sqrt(3)
a+c = 4
a = 4-c
4c-c^2 = 3sqrt(3)
本来解出a,c,由余弦定理可得b,但以上方程无解,要么我计算错误,要么你的题目有误

cosX + cosY = 2cos[ (X + Y) / 2 ] cos[ (X - Y) / 2 ]
cos（wx+π/3）+cos（wx-π/3) = 2coswx cospi/3 = coswx
f(x) = sqrt(3) sinwx + coswx - 1= 2 sin(wx + pi/6)) - 1
w = 2
f(B) = 1, sin(2B+pi/...

f（x）=根号3sinwx+cos（wx+π/3）+cos（wx-π/3）-1
=2cos(wx-π/3)-1
最小正周期为π 则w=2
f(x)=2cos(2x-π/3)-1
f(B)=2cos(2B-π/3)-1=1 B=π/6
向量BA×向量BC=|BA|*|BC|*cos(B)=ac*根号3/2=（3根号3...

连接BD
∵∠ABC=90°，D是AC中点
∴BD⊥AC，BD=AD，∠FBD=∠A=45°
∵DE⊥DF
∴∠BDF=∠ADE
∴△BDF≌△ADE
∴BF=AE=4，DE=DF
同理可得BE=CF=3
∴AB=7
∴S四边形DEBF=S△ABD=1/2*7*7/2=49/4