1)∵bsin(π/4 +C)-csin(π/4 +B)=a,
∴由正弦定理可得sinBsin(π/4 +C)-sinCsin(π 4 +B)=sinA.
∴sinB( √2sinC/2+ √2cosC/2)-sinC( √2sinB/2+ √2cosB/2)= √2/2 .
整理得sinBcosC-cosBsinC=1,
即sin(B-C)=1,
由于0<B,C<3π/4 ,从而B-C=π/2 .
(2)∵B+C=π-A=3π/4 ∴B=5π/8 ,C=π/8 ,
∵a= √2 ,A=π/4
∴b=asinB/sinA =2sin5π/8 ,c=asinC/sinA =2sinπ/8 ,
所以三角形的面积S=bcsinA/2= √2 sin5π/8 sinπ/8 = √2 cosπ/8 sinπ/8 =1/2
解:(1)证明:由bsin(
π
4 +C)-csin(
π
4 +B )=a,由正弦定理可得sinBsin(
π
4 +C)-sinCsin(
π
4 +B )=sinA.
sinB(
2
2 sinC+
2
2 cosC )-sinC(
2
2 sinB+
2
2 cosB )=
2
2 .
整理得sinBcosC-cosBsinC=1,
即sin(B-C)=1,
由于0<B,C <
3π
4 ,从而B-C=
π
2 .
(2)解:B+C=π-A=
3π
4 ,因此B=
5π
8 ,C=
π
8 ,
由a=
2 ,A=
π
4 ,得b=
asinB
sinA =2sin
5π
8 ,c=
asinC
sinA =2sin
π
8 ,
所以三角形的面积S=
1
2 bcsinA=
2 sin
5π
8 sin
π
8 =
2 cos
π
8 sin
π
8 =
1
2
解:(1)bsin(π/4+C)-csin(π/4+B)=a式由正弦定理得sinB*sin(π/4+C)-sinC*sin(π/4+B)=sinA,化简整理得sin(B-C)=1,则B-C=π/2
(2)有A=π/4和B-C=π/2以及A+B+C=π得B=5*π/8,C=π/8由正弦定理有b=a*sinB/sinA=2*sinB,c=a*sinC/sinA=2*sinC则△ABC的面积.=1/2*b*c*sinA=2*sinB*sinC*sinA=1/2