Question

Can someone help me answer a precalculus question please?

Answer 1

Find the angle between the given vectors to the nearest tenth of a degree.

u = <2, -4>, v = <3, -8>

Answer 2

@EducationsFinest

Answer 3

@Vocaloid

Answer 4

You can write u as 2i -4j and v as 3i -8j. Then you can apply the dot product rule to find the angle.

Take a look at this page:

http://www.wikihow.com/Find-the-Angle-Between-Two-Vectors

Or take a look at these videos. It will really make your base strong.

https://www.khanacademy.org/math/linear-algebra/vectors_and_spaces

Answer 5

you don't have to re-write them, this is really good compact notation you are using: \(\large \vec u = <2, -4>, \vec v = <3, -8>\)

for \(\large \vec u = <u_x, u_y>, \vec v = <v_x, v_y>\), we have
\(\large \vec u \bullet \vec v = u_x \times v_x + u_y \times v_y = |\vec u||\vec v| cos \theta\). \(\large \theta \) is the angle between these vectors.

\(\large |\vec u|\) is the magnitude of \(\large \vec u\) and equals \(\large \sqrt {u_x^2 + u_y^2}\), ditto for \(\large |\vec v|\).

that's all you need to answer this, but you should always check first for some trickery in the question, eg where they are clearly parallel.

Answer 6

@anikhalder thanks for the medal! have one back :p

Answer 7

Thank you very much. I really appreciate your explanation and I hope rather than the medals our mutual friend here won't be having troubles finding the angle between vectors anymore :)))

Answer 8

cool!

Answer 9

Thank you all!