(1 point) Find the angle between the plane z=0 and the plane passing through the points (0, 0, 0), (2, 3, 0), and (0, 3, 3)

i know when I have to vectors I can get the cosine the dot product but I don't know how to proceed with this question.I think using the cross products for the points might be a good way to solve it.

I used the cross product to find the normal vector of the second plane but im having problems with the first planes z=0 .I am assuming I and j are 1 each.

This one is not difficult either. There are two ways to go at it: 1) You can choose two vectors in the plane and calculate the cross product. As $(0,0,0)$ is in the plane choosing any two points on the plane gives you two vectors. Because $z=0$ is the only restriction, we can choose $x$ and $y$ freely. Thus $(1,0,0)$ and $(0,1,0)$ are possible vectors. Calculate the cross product and you are done. 2) You can argue geometrically and say that if $z=0$ then the plane is the $x$-$y$-plane. Hence its normal vector points in the direction of the $z$-axis. Hence $(0,0,1)$ is a normal vector