proof with dot and cross products

sambellamy

Junior Member
Joined
Oct 21, 2014
Messages
53
I am trying to prove this:

9438.jpg
What I have so far is here:

IMAG0509.jpg
Please help! I don't think that getting everything written out in terms of a1b1, etc is helpful as there will be nothing to cancel - each term would have four different components multiplied together. I think I am onto something with the |a||b| sin stuff, but I am not sure how to proceed. Any pointing in the right direction will be much appreciated. Thanks!
 
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