a = (1, 3, 2, 4)
b = (3, 1, -2, 4)
c = (4, 4, -1, -1)
The lengths of the three sides are
||b - a|| = the square root of 24
||c - b|| = 6
||c - a|| = the square root of 44
The angle at the vertex
a is approximately 1.05599 radians
b is approximately 1.29515 radians
c is approximately 0.79045 radians