How to fold a4 paper for 30 degree angle?

Question

I am trying to make a $30$ degree angle by folding an $A4$ paper, but I got nothing. It seems to be easy but I don't have a clue. I can make $A=45,B=67.5,C=67.5$ triangle or make $45 , \frac {45}{2} , \frac{45}{4}, \cdots$ by folding a right angle.
Is there any way to make a triangle with $30,60 ,90 $ degree by folding an $A4$ paper?
Remark: I search Google but there is almost nothing clear.
Remark2: I saw how to make an equilateral triangle, and then fold any angles to half is the answer. But my question is concerned with not using equilateral triangle.

Answer 1

1. Mark the centre line parallel to the long sides, by folding;
2. Fold one corner to this centre line, so that short side has one end on the centre line and one end in the original position;
3. This crease forms the hypothenuse of a 30-60-90 triangle.

The aspect ratio of the paper does not matter.

Back-of-the-envelope demo, using a similar C5 envelope:

Answer 2

A $30^\circ$-$60^\circ$-$90^\circ$ triangle has its short leg half the length of its hypotenuse. So, you just need to have a sidelength of length $1/2$ and a hypotenuse of length $1$. First make a square, then fold it in half to get a rectangle. Then, fold one of the corners so it touches the opposite side.