Question

The projections of a line on the co-ordinate axes are 4, 6, 12. The direction cosines of the line are

• A. $\frac{2}{7},\frac{3}{7},\frac{6}{7}$
• B. 2, 3, 6
• C. $\frac{2}{11},\frac{3}{11},\frac{6}{11}$
• D. None of these

Answer 1

Answer: (A)

$\frac{2}{7},\frac{3}{7},\frac{6}{7}$

Answer 2

cos²a + cos²b + cos²g =1

̃ 1 – sin²a + 1 – sin²b + 1 – sin²g =1

̃ sin²a + sin²b + sin²g = 2