Problem 1
In a convex quadrilateral of area , the sum of the lengths of two opposite sides and one diagonal is . Determine all possible lengths of the other diagonal.
Step 7 of 7: Conclude and verify existence
In plain words
The answer is unique even though the quadrilateral itself has many shapes.
Detailed analysis
Thus . Conversely, any with , placed perpendicularly on opposite sides of an -segment , gives a convex quadrilateral of area , so the value is attainable and unique.