写的不是很清楚:
m=(2√3sin(B/2),√3/2)---是吧?
n=(sin(B/2+π/2),1)
故:m·n=2√3sin(B/2)cos(B/2)+√3/2
=√3sinB+√3/2=√3
即:sinB=1/2,则:B=π/6或5π/6
是接着上面的把?B=π/6,S=(1/2)acsinB
=3csin(π/6)=3c/2=6√3,即:c=4√3
故:b^2=a^2+c^2-2accosB
=36+48-2*6*4√3*√3/2=12
即:b=2√3
写的不是很清楚:
m=(2√3sin(B/2),√3/2)---是吧?
n=(sin(B/2+π/2),1)
故:m·n=2√3sin(B/2)cos(B/2)+√3/2
=√3sinB+√3/2=√3
即:sinB=1/2,则:B=π/6或5π/6
是接着上面的把?B=π/6,S=(1/2)acsinB
=3csin(π/6)=3c/2=6√3,即:c=4√3
故:b^2=a^2+c^2-2accosB
=36+48-2*6*4√3*√3/2=12
即:b=2√3