# Pre-Cal

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Use the law of cosines to find the angle of Q between the given vectors.

v=3i + j w=2i - j

• Pre-Cal -

\vec b\cdot \vec c = \Vert \vec b\Vert\Vert\vec c\Vert\cos \theta

The law of cosines in vector form:

b dot c= abs b * abs c *CosA

(3i+j)dot(2i-j)=sqrt(10)*sqrt(5) CosA

CosA=5/5sqrt2= .707
solve for A

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