A dual graph is constructed by taking the original graph, which must be planar (no crossing edges) and creating a vertex inside each face of the graph. A face is an enclosed area in the graph and the space outside of the graph is also a face. Once you have created a vertex in every space, you must connect every vertex by crossing each edge in the original graph.

For example, a simple triangle is planar and has two faces, one inside and one outside. We would form a vertex inside the triangle and somewhere outside of the triangle. Now, we have three edges we must cross, so starting at the inner vertex, draw three lines with one exiting through exactly 1 side each. You should now have a vertex with 3 lines that exist outside of the triangle. Without crossing them, just simply connect them to the vertex on the outside. This will create a dual of the triangle. It should resemble two vertices connected with three edges. Note that this dual graph is not planar like the original.

I suggest looking at Saturnfans.com under the s-series section. Use the search button and you should find a graph

She had a dual nature because of the disease. This is a sentence containing the word dual.

the five graph is line graph,bar graph,pictograph,pie graph and coin graph

bar graph, double bar graph, line graph, and picto graph