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Accurim

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#7 - Angle between 2 vectors is [tex]\alpha[/tex] where cos[tex]\alpha[/tex] = [tex]\frac{3}{7}[/tex]. a = (2,3,-1) and b = ( -1, K, 1) use the 2 vectors and find possible values for K.

This is what I did:

[tex]a\bullet c = |a||b|cos\alpha[/tex]

(2,3,-1)[tex]\bullet (-1, k, 1) = \sqrt14\sqrt{2+k^2}\frac{3}{7}[/tex]

[tex]7k-7=\sqrt14\sqrt{2+k^2}[/tex]