A beetle crawled from vertex A straight to some point on edge ED then, likewise, down to vertex C so covering a distance double to the pyramid's altitude. Reconstruct the beetle's path. A good idea to start a resolution with is to look up the hint in the About Problem box: What is the pyramid's dimension? Let's have a look inside... Well then, it's a 4-side regular pyramid. In Geometria, one can neither draw nor measure anything inside a solid unless one cuts it. To uncover the altitude, cut through A, E, C. The fragments open up in their own windows. Now it's time to draw the altitude... and measure it. Want a tip? Select the line to measure (click over it), click right, then select Measure Distance from the popup menu. (Similar workarounds are available for the previous two operations.) Don't bother about the numerical result. Assign it to a variable and press the Write Down button. A Notepad record appears:     alt = |EF| Go back to the initial solid then select vertex A and edge ED in the above described manner. Lay distance alt off A to ED (most fields should have been automatically filled in by the previous selection). Draw lines AG and GC (e.g., select G, C, click right and select Draw Line from the popup menu). And here is the answer: AGC. You may review your resolution now. Pull aside the Resolution Log to uncover the solids' area, then go on pressing the Step Forth button.