0,88
Объяснение:
cosx=-9/16, x∈(π/2; π). sin(x/2)=?
Формула: sin²a=(1-cos2x)/2; sina=±√((1-cos2x)/2)
π/2<x< π⇒π/4<x/2< π/2⇒sin(x/2)>0
sin(x/2)=√((1-cosx)/2)=√((1-(-9/16))/2)=√(25/32)=5/4√2=5√2/8=0,883883476483184405501055...≈0,88
