2. You need to mark the blank slide with the "pie" symbol in mathematics: click "insert" and select "text box"; Select a text box from the pop-up menu, for example, a horizontal text box.
3. Draw a text box where you need to enter the "pie chart" symbol. Open the Insert tab and click the symbol.
4. Then a symbol dialog box will pop up. Click the "subset" triangle in the upper right corner and click "Greek and coptic language" in the pop-up menu. You will see the symbol "π" of "Pie" in the box below. Select it and click Insert.