Hope this helps.
The tick marks indicate they are of the same length, so each side is 12.
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.
(See photo2.jpg)
Solve for L using pythagoras. I find
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(See photo3.jpg)
That red line is half the length of the green line.
Therefore the red line has length:
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(See photo4.jpg)
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
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(See photo5.jpg)
A right angled triangle again, solving for the green side, which is finally .
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Man i was stupid. This is an equiliteral triangle. All these lines inside the triangle have length !! anyway you have the value for now...