Hi all,

I want to plot **a sphere and two planes** that are parallel to each other,

here is how it looks like from the slice of the sphere, the circle:

I try to read this:

this is my code and unable to plot the planes correctly:

```
using Plots; plotlyjs()
function sphere(r, C) # r: radius; C: center [cx,cy,cz]
n = 100
u = range(-π, π; length = n)
v = range(0, π; length = n)
x = C[1] .+ r*cos.(u) * sin.(v)'
y = C[2] .+ r*sin.(u) * sin.(v)'
z = C[3] .+ r*ones(n) * cos.(v)'
return x, y, z
end
# the equation of a plane in 3-space: ax + by + cz = d
# at least one of the numbers a, b, c must be nonzero
# the plane as the graph of a function z of x and y: z = -(a/c)x + (-b/c) y + d/c
# Given points P, Q, R in space, find the equation of the plane through the 3 points.
# P = (1, 1, 1), Q = (1, 2, 0), R = (-1, 2, 1).
# Solve with Gauss Elimination
# a + b + c = d
# a + 2b + 0c = d
# -a + 2b + c = d
function plane(x,y)
n = 100
x=range(-2,stop=2,length = n)
y=range(sqrt(2),stop=2,length = n)
f(x,y) = -y + 5
plot!(x,y,f,st=:surface,c=my_cg,camera=(-30,30))
end
my_cg = cgrad([:red,:blue])
surface(sphere(2, [1,2,3]), c=my_cg)
surface(plane(0,1))
# using LinearAlgebraX
#A = [1 2 3 1;
# 0.5 2 3 1;
# 1.5 2 3 1]
# rrefx(A)
# Solution $a=0, b=1, c=1, d=5$
#Change result to Float
# Float64.(rrefx(A))
```

I have made an improvement a bit, if I could finish it alone I will post it here.