That would turn it into an octagon.
If you mean the base has 4 sides then the pyramid is a square based pyramid and has 5 corners. If you mean the pyramid has 4 faces then the pyramid is a tetrahedron with a triangular base and has 4 corners.
An example of a 90 degree angle is any of the four corners of an A4 page.
By cutting off two of its corners which will leave you with 2 triangles and 1 pentagon.
To do something in way that is the cheapest and easiest.
This comes from the EARLY metal roofing trades. Cutting corners (literally) instead of double seaming / folding every seam.
it is used for cutting corners
Cuts - 2005 Cutting Corners 1-1 was released on: USA: 14 February 2005
On ours, the cutting out was fairly random - at higher speeds not linked to corners - but it was cured by replacing the injectors. Expensive...
hexagon
You have to modify square gutter corners by either cutting and subtracting from them to reduce the angle, or combining two corners to increase the angle. You can always fabricate your own from straight gutter.
Cutting corners on materials.
By "corners", do you mean vertices or edges?
Adjacent corners of a square share one side. Opposite corners share no sides.
That would turn it into an octagon.
Insufficient analysis, cutting intellectual corners or too much generalisation from low grade data.
if you mean "vertices" by "corners" then sixteen