PK*PTSINA=18
PT/SIN(A+B)=PK/SINB
PT=PK*SIN(A+B)/SINB
PK^2*SINA*SIN(A+B)/SINB=18
PK=SQRT(18*SINB/SINA*SIN(A+B))
PK/2SINB=R
R=3sqrt(2/sina*sinb*sin(a+b))
PK*PTSINA=18
PT/SIN(A+B)=PK/SINB
PT=PK*SIN(A+B)/SINB
PK^2*SINA*SIN(A+B)/SINB=18
PK=SQRT(18*SINB/SINA*SIN(A+B))
PK/2SINB=R
R=3sqrt(2/sina*sinb*sin(a+b))