collocation
points
21
γ
25
ϕ
2
0
.
8
b
6
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
-
1
.
0
-
0
.
5
0
.
0
0
.
5
1
.
0
0
2
4
6
8
x
u
and
uv
