TADM2E 6.15
From Algorithm Wiki
No. Any graph with a min path tree not satisfying the triangular inequality will not have this property. There is a constant k that you can add to all edges so that the triangular inequality will hold.
Example:
A-1-B
A-3-C
B-1-C
B-4-D
C-1-D
Note that the triangular inequality does not hold between B and D, as you can pass through C. The min path tree from B here is:
B-A
B-C
C-D
Now add k=10. Now the triangular inequality does hold between B and D. The min path tree from B is:
B-A
B-C
B-D