A quadrilateral has 2 diagonals. It does not matter whether it is convex or not.
What is the sum of the measures of the angles of a convex quadrilateralwill this property hold if the quadrilateral is not convex?
It depends on whether you mean area, perimeter, sides, angles, diagonals, etc.
It may or may not be.
how many sides convex quadilaterals have
A concave quadrilateral. An arrowhead or a delta, for example.
The sum of the interior angles of a quadrilateral is 360 degrees (not 180). The sum of the exterior angles is also 360 degrees. Whether the quadrilateral is convex or concave is not relevant.
It would be a concave quadrilateral The link below has some pics.
A concave quadrilateral would be a non-convex quadrilateral. * * * * * Also known as delta or arrowhead or chevron.