# Thread: Vector Q - Planes and angles

1. ## Vector Q - Planes and angles

Hi could someone pls help me with this...

If I have a line:

3x-2=4y-5=-z+2

and a normal:

r(5,-4,1)

how would I calculate the angle between them?

If you could show me how... I will do the rest

many thanks

2. I should think it would suffice to find any vector $\bf{a}$ in the direction of your line and calculate

$
\cos\theta = \frac{\bf{a}\cdot\bf{r}}{|\bf{a}||\bf{r}|}
$

To find such an $\bf{a}$, just find two points on your line and find the vector pointing between them.

What do you think? I'm not 100% sure so be critical!