Let `veca` and `vecb` be unit vectors that are perpendicular to each other, then `[veca+(veca xx vecb)+(veca xx vecb)]` is equal to

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)`