Question

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

Answer 1

Answer:

dot product between A and B vector is zero.

hence angle between these two is 90 deg

Explanation:

Answer 2

Answer:

$\cos \alpha \\ = \frac{a.b}{ |a| \times |b| } \\ = \frac{( - 2i + 3j + k)(i + 2j - 4k)}{ \sqrt{( - 2) {}^{2} + 3 {}^{2} + {1}^{2} } \times \sqrt{ {1}^{2} + {2}^{2} + ( - 4) {}^{2} } } \\ = \frac{ - 2 + 6 - 4}{ \sqrt{4 + 9 + 1} \times \sqrt{1 + 4 + 16} } \\ = \frac{0}{ \sqrt{14} \times \sqrt{21} } \\ = 0$

therefore,

$\cos( \alpha ) = 0 \\ = > \cos( \alpha ) = \cos(90) \\ = > \alpha = 90$

hope this helps ☺️