# Thread: Vectors - determine "k"

1. ## Vectors - determine "k"

Hi,

Can someone help guide me towards solving this question?

This is what I've done so far:

- otownsend

2. ## Re: Vectors - determine "k"

try solving

$\cos(60^\circ) = \dfrac 1 2 = \dfrac{v_1 \cdot v_2}{\|v_1\|\|v_2\|}$

where $v_1 = (1,1),~v_2 = \left(1,-\dfrac 1 k\right)$