math - Finding angle between two unit vectors in three dimensions -

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i trying basic 3d simulation has been 20 years since learned stuff in high school...

if have 2 vectors in 3 dimensions, how find angle between them. example have 1 vector of (3,2,1) , of (4,-5,6) how find angle (in degrees or radians) between them. if recall there formula this.

thanks.

here go


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