If  l_1, m_1, n_1 and l_2, m_2, n_2 be the direction cosines of two concurrent lines. Then the direction cosines

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Q 1207134088.     If  l_1, m_1, n_1 and l_2, m_2, n_2 be the direction cosines of two concurrent lines. Then the direction cosines of the line bisecting the angles between them are proportional to
A

l_1 + l_2, m_1 + m_2, n_1 + n_2

B

l_1 l_2, m_1 m_2, n_1 n_2

C

l_1 - l_2, m_1 - m_2, n_1 - n_2

D

m_1 n_2 + m_2 n_1, n_1 l_1 + n_2 l_2 , l_1 m_2 + l_2 m_1

#### HINT

(Provided By a Student and Checked/Corrected by EXXAMM.com Team)

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