4' wide by 4' tall How long would the angle be to connect the two on a right triangle

The corners would be 45 degree angles since the 2 sides (assuming they connect to form a 90 degree angle). Since 180-90=90 and te 2 sides are the same, you would divide 90 by 2 which equals 45 degrees. Therefor you would have two 45 degree angles.