find the angle between the two vectors.
u = (2, -4)
v= (3, -8)
I got 38/ the sqr. root of 20 times 5 after doing the dot product but my calculator keeps saying error when I multiply that with the arcos

Question

find the angle between the two vectors. 
u = (2, -4)
v= (3, -8) 
I got 38/ the sqr. root of 20 times 5 after doing the dot product but my calculator keeps saying error when I multiply that with the arcos

parthkohli · Answer

So you calculated the dot product and then divided that by the product of magnitudes, then took the arcos. Correct?

mathmale · Answer

Let's do it by hand to see whatever might be going wrong.

parthkohli · Answer

The dot product comes out to be 38. The magnitude of u is root(20) and the magnitude of v is root(73). So yeah, he has been incorrect till now.

parthkohli · Answer

There is no arcos of what you wrote.

anonymous · Answer

I know but once you get the answer to find the angle I believe you take that and do the arcos

parthkohli · Answer

Yes, but you have gotten the incorrect result till now.

anonymous · Answer

i got it! its 6 degrees. thank you!!!!!!!!!!!!

parthkohli · Answer

Yup!