How to calculate the dip and dip direction of intersection line of 2 planes?

The equation of a plane is like Ax + By + Cz + D = 0.

The other plane is Ex + Fy + Gz + H = 0 .

The intersection is the line where both equations are equal.

Ax + By + Cz + D = Ex + Fy + Gz + H

So you rewrite this in the form of a line.

(A - E)x + (B - F)y + (C - G)z + D - H = 0

Now you analyze the slope any way you know how.