Hope this helps.
Because each side is split in the middle we know that each is 6 units.
We also know that the 3 corners of the triangle each have because all side lengths are the same, meaning it's equilateral.
So for our seperate triangles we have angles, right angles and 6 unit lengths, which is enough for trigonometry.
Though if you're looking for a solution using Pythagorean theorem then I'll take another look.
Solve for L using pythagoras. I find
That red line is half the length of the green line.
Therefore the red line has length:
We once again have a nice right angled triangle to work with.
We have two sides so solve for the third(green) one.
The green side is
A right angled triangle again, solving for the green side, which is finally .
Man i was stupid. This is an equiliteral triangle. All these lines inside the triangle have length !! anyway you have the value for now...