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JEE-MAIN 2019
12-01-2019 S1
Question
A 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 $O P Q$ and $P Q R$ is
Select the correct option:
A
(1) $\cos ^{-1}\left(\frac{19}{35}\right)$ (2) $\cos ^{-1}\left(\frac{9}{35}\right)$ (3) $\cos ^{-1}\left(\frac{17}{31}\right)$ (4) (1) $\cos ^{-1}\left(\frac{19}{35}\right)$ (2) $\cos ^{-1}\left(\frac{9}{35}\right)$ (3) $\cos ^{-1}\left(\frac{17}{31}\right)$ (4) $\cos ^{-1}\left(\frac{7}{31}\right)$(1) $\cos ^{-1}\left(\frac{19}{35}\right)$ (2) $\cos ^{-1}\left(\frac{9}{35}\right)$ (3) $\cos ^{-1}\left(\frac{17}{31}\right)$ (4) $\cos ^{-1}\left(\frac{7}{31}\right)$
B
$\cos ^{-1}\left(\frac{9}{35}\right)$
C
$\cos ^{-1}\left(\frac{17}{31}\right)$
D
$\cos ^{-1}\left(\frac{7}{31}\right)$
✓ Correct! Well done.
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Solution
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