0

I'm trying to prove the identity $$a \times (\nabla \times a) = 1/2\nabla (a^2)-(a\cdot\nabla)a$$ But using the BAC-CAB rule I only get: $$a \times (\nabla \times a) = \nabla (a^2)-(a\cdot\nabla )a$$ I don't know why must be a factor $1/2$ on the right side of the equal sign. Could anyone help me, please?

Caue Evangelista
  • 81
  • 1
    See http://math.stackexchange.com/questions/1437060/textbfa-times-nabla-times-textbfa-with-index-notation?rq=1 ; http://math.stackexchange.com/questions/942082/prove-frac12-mathbf-nabla-u-cdot-u-u-times-nabla-times-u-u?rq=1 – Winther Feb 19 '17 at 14:52
  • Thank you very much Winther!!!! – Caue Evangelista Feb 19 '17 at 15:35

0 Answers0