Like this?
I don't think this works for most unfortunately
[![enter image description here][1]][1]
You draw the diagonals and then draw a line through the middle pentagon
I have used an irregular pentagon here and the green line is the half line
You have to use your brain where you draw the line, for instance oleslaw gave the example:
[![enter image description here][2]][2]
Where it obviously isn't equal, however it would be if you draw the line more horizontally through the middle pentagon [1]: https://i.sstatic.net/faIJP.png [2]: https://i.sstatic.net/43SPf.png