the shortest distance between two points is usually a straight line, but in your case spending a bit more on the line and arching out an around the spruce is a great solution. the farther you can stay outside the outer edge of the foliage the better, you will damage fewer and finer roots. If moving the trench is not possible and you really want to save the spruce, consider a horizontal boring machine that can put the cable several feet below the root system boring directly in that straight line.
