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AP EAMCET · Maths · Three Dimensional Geometry

Let \(A(1,-1,2), B(6,11,2), C(1,2,6)\) be three points. If \(l_1, \mathrm{~m}_1, \mathrm{n}_1\) are the direction cosines of \(\mathrm{AB}\) and \(l_2, \mathrm{~m}_2, \mathrm{n}_2\) are the direction cosines of \(\mathrm{AC}\), then \(\left|l_1 L_2+\mathrm{m}_1 \mathrm{~m}_2+\mathrm{n}_1 \mathrm{n}_2\right|=\)

  1. A \(\frac{63}{65}\)
  2. B \(\frac{36}{65}\)
  3. C \(\frac{16}{65}\)
  4. D \(\frac{13}{64}\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(\frac{36}{65}\)

Step-by-step Solution

Detailed explanation

Direction ratios of \(A B\) are \(a_1=6-1=5, b_1=11-(-1)=12, c_1=2-2=0\) Direction ratio's of \(A C\) are…