Problem 653

Sir SagarApril 6, 20150

Find the appropriate angle between the vectors.

u = (3, -5, 2), and (-9, 5, 1)

Solution:-

To find the angle we use the identity $u\cdot v=\left | u \right |\left | v \right |cos\Theta .$

$cos\Theta =\frac{(\left | u \right |\left | v \right |)}{(u\cdot v)} =\frac{-50}{\sqrt{38}\sqrt{107}}$

= $\Theta \approx 2.47radians \approx 141^{\circ}$

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