I feel a little silly asking this - I guess I should've paid more attention in geometry class years ago...

And I can't seem to find an answer searching the internet - probably, I'm searching wrong.

I am building a 4X8' chicken tractor with a triangular roof. I figure that, using 4' 2X4s to make the sides/roof, I'll create an equilateral triangle, so all of my inside angles would be 60*. My bottom frame is a flat 2X4, so to get the inside angle of 60*, I need to cut the side 2X4s at 30* on the bottom to get them to lean in correctly so they meet at the top. At the top, where they meet, they'd need to be cut at 60* to get them to join flush with one another. That's my theory, anyway, and I hope this makes at least a little sense...

How do I calculate how much to cut off the end of the 2X4 to create the correct angles? I tried calculating this, and was way off the first time, so I recalculated and thought I fixed it, and they still wouldn't meet up correctly. I don't have a miter saw, just a circular saw and a jigsaw.

I'm starting to think I shoud've just built a rectangular box, but I'm already into this project, and shoot, it can't be that hard...? I'm just a little math-challenged. Last fall, I managed to build the horses a pretty respectable 12X24 run-in shed, but that was all right angles...

Thanks for any help!

Diana