vector a = (2,5) and vector b = (-1,t)

solve for t when the vectors have a 45 degree angle between them

any help would be appreciated. :)

- Jan 11th 2011, 08:57 AMcoloradosolve for variable when vector a and b have a 45 degree angle between them
vector a = (2,5) and vector b = (-1,t)

solve for t when the vectors have a 45 degree angle between them

any help would be appreciated. :) - Jan 11th 2011, 09:08 AMe^(i*pi)
If I remember correctly you can use the dot product

- Jan 11th 2011, 09:27 AMcolorado
hm, yeah thats what I figured. I can't figure out how to solve from there on.

- Jan 11th 2011, 09:28 AMProve It
Where are you having trouble? It just ends up becoming a quadratic after you square both sides.

- Jan 11th 2011, 09:32 AMe^(i*pi)

This one does factor but it might be easier to use the quadratic formula - Jan 11th 2011, 10:03 AMcolorado
I tried that but Ididn't get the correct answer. the answer is t=7/3

- Jan 11th 2011, 10:24 AMQuacky
Yes, that is the positive answer you get when you solve the quadratic.

- Jan 11th 2011, 10:29 AMcolorado
ah okay, i'll give it another go

- Jan 11th 2011, 10:35 AMQuacky
I've editted the post. Where was your mistake? I assume it was probably just a sign error or something.

- Jan 11th 2011, 11:32 AMmr fantastic
- Jan 11th 2011, 12:42 PMcolorado
noted