If `vecb` is not perpendicular to `vecc` . Then find the vector `vecr` satisfying the equation `vecr xx vecb = veca xx vecb and vecr. vecc=0`

Explanation

Given `vecrxxvecb=vecaxxvecbRightarrow (vecr-veca)xxvecb=0`
Hence, (`vecr - veca) and vecb` are parallel.
`Rightarrow vecr-veca=tvecb`
`vecr.vecc=0`
Therefore, taking dot product of (i) by `vecc`, we get `vecr.vecc -veca.vecc=t(vecb .vecc)`
`or 0-veca.vecc=r(vecb.vecc)ort=-((veca.vecc)/(vecb.vecc))`
from (i) and (ii) solution of `vecr" is " vecr =veca-((veca.vecc)/(vecb.vecc))vecb`