Inkscape is a "free treasure," if there is such a thing. My thanks to all who have spent countless hours bringing this powerful vector graphics editor to all of us freely.
I struggled to learn how to make a simple symmetrical trapezoid in Inkscape. I found the answer here but it took some searching.
- Draw a rectangle.
- Convert it to a path (Path > Object to Path)
- Use the node select tool (F2) to select the two corners of the rectangle that you want to adjust to form a trapezoid (You have to hold down the shift key to select multiple nodes).
- Press the comma or period keys to move apart or bring together the nodes.
Step 4 doesn't seem to be well documented, but it sure is a handy trick!