Let O be the origin and` vec(OX) , vec(OY) , vec(OZ)` be three unit vector in the directions of the sides `vec(QR) , vec(RP),vec(PQ)` respectively , of a triangle PQR.
`|vec(OX)xxvec(OY)|=`
A. sin (P + Q)
B. sin 2R
C. sin (P+R)
D. sin (Q+R)
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