1.

Prove that a necessaryand sufficient condition for three vectors ` vec a , vec b`and ` vec c`to becoplanar is that there exist scalars `l , m , n`not all zerosimultaneously such that `l vec a+m vec b+n vec c= vec0dot`

Answer» Here, it is given that ,
`lveca+mvecb+nvecc = 0`
If we put, `l =-1 , m = x and n = y`, then,
`-veca +xvecb+yvecc = 0`
`=> veca = xvecb+yvecc`, which is the neccessary condition for all three vectors to be coplanar.
Now,
`lveca+mvecb+nvecc = 0`
`=>lveca = -mvecb-nvecc`
`=>veca = -m/lvecb-n/lvecc`, which is the sufficient condition for all three vectors to be coplanar.



Discussion

No Comment Found

Related InterviewSolutions