SinAsinC=3/4。

And b 2 = AC, namely sin 2b = sinasinc = 3/4.

SinB= root sign 3/2, B=60 degrees.

sinA+sinC = sinA+sin( 120-A)= sin(A+60)

Because A< 120

60 & lta+60 & lt； 180

0 & ltsin(A+60 )≤ 1

0< Sina +sinC≤ 1