a bentech presentation
Angle between two planes

Plz drag foot of normals to bring together at the edge

B = (9.244114796443267, 13.293922244179349)
C = (9.872250740412506, -7.144747281121056)
D = (9.121645771289593, -25.894988763435798)
f = Segment(C, D)
G = (-1.807717887636783, 13.440304925475417, 0)
g = Line(G, B)
h = Line(C, D)
a = Plane(g, f)
A = (5.598603825622411, 10.384854414476003)
E = (9.950508721246056, 2.1248625106398045)
i = Line(A, E)
F = Point(g)
c = 2.1 (slider from -5 to 5, step 0.1)
b: y + (c * z) = 7
j = IntersectPath(b, a)
I = PointIn(b)
k = OrthogonalLine(I, b)
J = PointIn(a)
l = OrthogonalLine(J, a)
K = Point(k)
L = Point(l)
u = Vector(I, K)
v = Vector(J, L)