Archive
7th of September 2015
Mathematics
Q:

Sir , how to prove that 3 points with position vectors -2 i + 3 j + 5 k , i + 2 j + 3 k and 7 i - k are collinear ?? i ,j & k are orthogonal unit vectors

Aditya - JEE-Basic - Class VI

Monday, September 07, 2015 at 18:16:PM

A:

C o n s i d e r space t h e space v e c t o r s A equals negative 2 i with overbrace on top plus 3 j with overbrace on top plus 5 k with overbrace on top B equals i with overbrace on top plus 2 j with overbrace on top plus 3 k with overbrace on top C equals 7 i with overbrace on top minus k with overbrace on top N o w space c o n s i d e r B minus A equals open parentheses i with overbrace on top plus 2 j with overbrace on top plus 3 k with overbrace on top close parentheses minus open parentheses negative 2 i with overbrace on top plus 3 j with overbrace on top plus 5 k with overbrace on top close parentheses space space space space space space space space space equals 3 i with overbrace on top minus j with overbrace on top minus 2 k with overbrace on top C minus A equals open parentheses 7 i with overbrace on top minus k with overbrace on top close parentheses minus open parentheses negative 2 i with overbrace on top plus 3 j with overbrace on top plus 5 k with overbrace on top close parentheses space space space space space space space space space equals 9 i with overbrace on top minus 3 j with overbrace on top minus 6 k with overbrace on top space space space space space space space space space space equals 3 open parentheses 3 i with overbrace on top minus j with overbrace on top minus 2 k with overbrace on top close parentheses space space space space space space space space space space equals 3 open parentheses B minus A close parentheses T h u s comma space C minus A space i s space p r o p o r t i o n a l space t o space B minus A H e n c e space A comma B space a n d space C space a r e space c o l l i n e a r.

Monday, September 07, 2015 at 18:29:PM