If `veca,vecb,vecc` be unit vectors such that `veca.vecb=veca.vecc=0` and the angle between `vecb` and `vecc` is `pi//6`. Prove that `veca=pm2(vecbxxvecc)`

Explanation

We have `veca.vecb = veca .vecb =0`
This implies that `veca` is perpenedicular to both `vecb and vecc`. Thus, `veca` is a unit vector, perpendicular to both `vecb and vecc`.Hence,
`vecr = +-(vecb xx vecc)/(|vecbxxvecc|) = +-(vecbxxvecc)/(|vecb||vecc|sinpi//3)`
` = +- 2 (vecb xx vecc)`