Question

Quick check? Thank You for helping!

Use the formula v1*v2=|v1||v2|cos theta to find the cosine of the angle between the two vectors (-7,8) and (5,3).

I got cos theta=-11/61.97. Is this correct? Thanks!

Answer 1

@nincompoop @Michele_Laino @ganeshie8 @campbell_st @zepdrix @Luigi0210 @Destinymasha @radar @Whitemonsterbunny17

Answer 2

I also solved for theta, getting 100.22 degrees.

Answer 3

we can write this:
\[\left\| {{v_1}} \right\| = \sqrt {49 + 64} = 10.63\]
\[\left\| {{v_2}} \right\| = \sqrt {25 + 9} = 5.83\]
\[{v_1} \cdot {v_2} = - 35 + 24 = - 11\]
so we get:
\[\cos \theta = \frac{{ - 11}}{{10.63 \times 5.83}}\]

Answer 4

so same thing, awesome!

Answer 5

Thanks for the confirmation!

Answer 6

yes!
\[\cos \theta = \frac{{ - 11}}{{10.63 \times 5.83}} = - \frac{{11}}{{61.97}}\]

Answer 7

:)