plzzz help
find the angle between the vectors, approximate your answer to the nearest tenth: v=-5i-3j, w=2i-4j.
A.85.6 degrees
B.5.1 degrees
C.147.5 degrees
D.32.5 degrees

Question

plzzz help
find the angle between the vectors, approximate your answer to the nearest tenth: v=-5i-3j, w=2i-4j.
A.85.6 degrees
B.5.1 degrees
C.147.5 degrees
D.32.5 degrees

misty1212 · Answer

hi
take the dot product
divide by the product of the absolute values
take the inverse cosine
you know how to get a dot product?

misty1212 · Answer

it is very easy also very easy to cheat http://www.wolframalpha.com/input/?i=%28-5i-3j%29dot%282i-4j%29

anonymous · Answer

Can you take me through the steps plz

misty1212 · Answer

but not really necessary 
$$-5\times 2+-3\times (-4)=-10+12=2$$

misty1212 · Answer

you see how i got that ?

anonymous · Answer

yes

misty1212 · Answer

ok now we need the absolute value of each one

misty1212 · Answer

for the first one it is 
$$\sqrt{5^2+3^2}=\sqrt{25+9}=\sqrt{34}$$

misty1212 · Answer

for the second one it is 
$$\sqrt{4^2+2^2}=\sqrt{16+4}=\sqrt{20}$$

misty1212 · Answer

we can simplify those but no matter you are going to have to use a calculator anyways

misty1212 · Answer

http://www.wolframalpha.com/input/?i=arccos%282%2Fsqrt%28680%29%29

anonymous · Answer

$$2\sqrt{5}$$

misty1212 · Answer

looks like $85.6^\circ$

anonymous · Answer

i thought I was suppose to break down the 20

misty1212 · Answer

like i said it doesn't really matter because you can’t do this without a calculator

anonymous · Answer

oooo ok thank you so much :)

misty1212 · Answer

you are welcome, glad to help