## anonymous one year ago Use the formula v1 x v2 = absltvalue v1 x absltvalue v2 to find the cosine of the angle between the two vectors (-7,8) and (1,0).

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1. misty1212

hi!!

2. misty1212

you got the length of each of these?

3. misty1212

dot product should be easy since because of the $$(1,0)$$ it is just $$-7$$

4. anonymous

So Im just curious in the equation when it says multiply v1 by v2 does that mean you multiply the x and y values of (-7,8) and (1,0) together and than add the x and y values together?

5. dumbcow

^^ yes $v_1*v_2 = (x_1,y_1) * (x_2,y_2) = x_1 *x_2 + y_1*y_2$

6. anonymous

so the equation would come out to be -7=7costheta. Which would then simplify down to -1=costheta. Then you solve for theta giving you 180 degrees?

7. anonymous

@dumbcow

8. dumbcow

equation is $\cos \theta = \frac{v_1 *v_2}{|v_1| |v_2|}$ $\cos \theta = \frac{-7}{\sqrt{113}}$ $\theta \approx 131.2$