Given tetrahedron *PQRS* with the area of face *PQR* being *A*_{1}, the area of face *PQS* being *A*_{2},
the length of side *PQ* being *x*, and the angle between faces *PQR* and *PQS* being *θ,* find a formula for the volume of
tetrahedron *PQRS* in terms of *A*_{1}, *A*_{2}, *x*, and *θ*.