Question

The angle between two vectors -2i+3j+k and 2i+2j-4k

Answer 1

Answer:

$\cos( \alpha ) = \frac{( - 2i + 3j + k)(2i + 2j - 4k)}{ | - 2i + 3j + k| |2i + 2j - 4k| } = \frac{ - 4 + 6 - 4}{ \sqrt{4 + 9 + 1} \sqrt{4 + 4 + 16} } = \frac{ - 2}{ \sqrt{14} \sqrt{24} } = \frac{ - 1}{ \sqrt{14} \sqrt{6} } = - \frac{1}{ \sqrt{84} }$