1.设角BAD=t,则sin(90+t)=2根号2/3=cost
由余弦定理：BD^2=(3根号2)^2+3^2-2*3根号2*3cost=3
所以BD=根号3.
2.AB+2BC=c+2a,而已知b/sinb=根号3/(根号3/2)=2,所以a=2sinA,b=2sinB.
故c+2a=2[sinC+2sinA]=2[sinAcosB+cosAsinB+2sinA]=5sinA+根号3cosA=2根号7*sin(A+t).
因为2π/3>A>0,而t
1.设角BAD=t,则sin(90+t)=2根号2/3=cost
由余弦定理：BD^2=(3根号2)^2+3^2-2*3根号2*3cost=3
所以BD=根号3.
2.AB+2BC=c+2a,而已知b/sinb=根号3/(根号3/2)=2,所以a=2sinA,b=2sinB.
故c+2a=2[sinC+2sinA]=2[sinAcosB+cosAsinB+2sinA]=5sinA+根号3cosA=2根号7*sin(A+t).
因为2π/3>A>0,而t