He might only have dimensional lumber (1x3).With that cut, I would be more concerned with length than width. If you plan to cut the board in 1/2, you still have nearly an 3/4ths of an inch of material on either side of the blade. This is plenty and should not be a problem.
Set your fence to the desired distance from the blade (obviously tip it 45 degrees) and use feather boards and hold downs similar to this. Also use push sticks or blocks like these or these. Do a google search for feather boards, hold downs, push sticks and push blocks to get an idea of what is out there, and use what fits your work and tools.
Alternatively, you could cut a 45 degree cut on one edge of the board and then rip off the opposing edge with the blade straight. This would be marginally safer, but result in more wasted wood. You would use feather boards, hold downs, push sticks and push blocks in the same manner as described above.
With hold downs and push sticks, this shouldn't be a problem on a reasonably equipped table saw. The work piece is held down and your hands are well away from the blade.
It really doesn't make much difference. The process will be the same, the safety aspect only slightly greater with the less wide the board.I'm at a loss.
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