Let ` vec aa n d vec b` be unit vectors that are perpendicular to each other. Then `[ vec a+( vec axx vec b) vec b+( vec axx vec b) vec axx vec b]` will always be equal to `1` b. `0` c. `-1` d. none of these

Options

A. 1
B. 0
C. `-1`
D. none of these

Answer

a

Explanation

`[ veca + (hata xx vecb) vecb + (veca xx vecb) veca xx vecb]`
` (veca + (veca xx vecb)) . (( vecb + (veca xx vecb))xx (veca xx vecb))`
` (veca + (veca xx vecb)) . (vecb xx (veca xx vecb))`
` (veca + (veca xx vecb)) . (veca- (veca.vecb) vecb)`
`veca. veca =1 " " (as veca. vecb =0, veca, (veca xx vecb) =0)`