2. Draw an image of a mathematician on a postcard. Simple geometric figures or lines can be used to express the characteristics of mathematicians, such as glasses, ties and hairstyles.
3. Add some elements related to mathematics beside mathematicians, such as numbers, formulas, graphs, etc., to highlight the identity and subject characteristics of mathematicians.
4. Write greetings or mathematician-related words on postcards. You can choose to write by hand or print with a printer.
Finally, put a stamp and mailing address on the postcard and send it out.