Decoding the LaTeX that didn't render, we seek sum of the angles of the seventh roots of
That's on the unit circle, 45 degrees into the third quadrant, aka 225 degrees.
The seventh roots will all be separated by 360/7, around 51 degrees. The first seventh root has
That's around 32 degrees.
The next angle is
The next one is
and in general
The first sum is just -135° since it's one seventh of the sum of seven -135s.
We have 1+2+3+4+5+6+7 = (1+7)+(2+6)+(3+5) + 4 = 28 so
If I didn't screw it up, that means the answer is
Answer: 1305°