MathematicsMedium249×since 2002Q2574A tetrahedron has vertices P(1, 2, 1), Q(2, 1, 3), R(–1, 1, 2) and O(0, 0, 0). The angle between the faces OPQ and PQR is :Acos^−-−1(1731)\left( {{{17} \over {31}}} \right)(3117)Bcos^−-−1(935)\left( {{{9} \over {35}}} \right)(359)Ccos^−-−1(1935)\left( {{{19} \over {35}}} \right)(3519)Dcos^−-−1(731)\left( {{7 \over {31}}} \right)(317)Check answerSkip