Make a centre crease down the length of the paper then open it up.
Next fold one corner over and onto the centre crease so that the fold line passes through the corner next to it (on the short side of the paper).
You have created some angles of 60 degrees and of 30 degrees.
Can you prove this?
As a further challenge you amy like to fold a sheet of paper into an equilateral triangle.
Download the equilateral triangle paper folding instructions here.