120 Degrees
Rotate that triangle.
Start file
1 9 2 8 3 7 6 5 4
End file
4 3 5 2 6 1 9 8 7
View Diff
1,4c1,4 < 1 < 9 2 < 8 3 < 7 6 5 4 --- > 4 > 3 5 > 2 6 > 1 9 8 7
Solutions by @quadface:
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