Angle of intersection of the line and the plane

I got this homework question that I do not understand. It is as followed;

Suppose a line intersects a plane at one point. Define what is meant by the "angle of intersection of the line and the plane". Describe a method you can use to determine the angle of intersection of a line and a plane. Then use your method to calculate the angle of intersecction of the given live and plane.

$\displaystyle (x/2) = ((y-1)/1) = ((z+1/-1)$ and x + 2y + 3z - 4 = 0.

I believe the angle of intersection of the line and the plane is the angle the line and plane insect at. There will always be two angles that will always add up to 180$\displaystyle ^o$ and can be modeled mathematically by the formula of $\displaystyle cos(-) = (m1 dot m2)/(|m1||m2|)$

However, to find the angle they intersect at I have no idea because there is only one directional vector. For the formula to work you need two. How do I get the other one? To I find two points that will make the right equation equal to zero and get the second directional vector there?

Also, is my explanation of "angle of intersection of the line and the plane" is correct? Is it detailed enough?