Answer:
The minimum possible length of such a line is 8 cm
Step-by-step explanation:
If we had a rectangle, we can name each side "a" and "b".
The area of the rectangle will be:

Note: This is the constraint of our optimiztion problem.
Applying the Pitagoras theorem, the line, as in the figure attached, will have a length of:

We can replace "a" as a function of "b":

Then,

To calculate the minimum length, we derive and equal to zero:
![dL/db=\frac{d}{db} [(\frac{1024}{b^2}+b^2)^{\frac{1}{2}} ]\\\\dL/db=\frac{1}{2} (\frac{1024}{b^2}+b^2)^{(-\frac{1}{2})}\cdot \frac{d}{db} [\frac{1024}{b^2}+b^2]\\\\ dL/db=\frac{2b+1024\cdot(-2)\cdot b^{-3}}{2\sqrt{(\frac{1024}{b^2}+b^2)}} \\\\\\ dL/db=\frac{2b-2048\cdot b^{-3}}{2\sqrt{(\frac{1024}{b^2}+b^2)}}](https://tex.z-dn.net/?f=dL%2Fdb%3D%5Cfrac%7Bd%7D%7Bdb%7D%20%5B%28%5Cfrac%7B1024%7D%7Bb%5E2%7D%2Bb%5E2%29%5E%7B%5Cfrac%7B1%7D%7B2%7D%7D%20%20%5D%5C%5C%5C%5CdL%2Fdb%3D%5Cfrac%7B1%7D%7B2%7D%20%28%5Cfrac%7B1024%7D%7Bb%5E2%7D%2Bb%5E2%29%5E%7B%28-%5Cfrac%7B1%7D%7B2%7D%29%7D%5Ccdot%20%5Cfrac%7Bd%7D%7Bdb%7D%20%5B%5Cfrac%7B1024%7D%7Bb%5E2%7D%2Bb%5E2%5D%5C%5C%5C%5C%20dL%2Fdb%3D%5Cfrac%7B2b%2B1024%5Ccdot%28-2%29%5Ccdot%20b%5E%7B-3%7D%7D%7B2%5Csqrt%7B%28%5Cfrac%7B1024%7D%7Bb%5E2%7D%2Bb%5E2%29%7D%7D%20%5C%5C%5C%5C%5C%5C%20dL%2Fdb%3D%5Cfrac%7B2b-2048%5Ccdot%20b%5E%7B-3%7D%7D%7B2%5Csqrt%7B%28%5Cfrac%7B1024%7D%7Bb%5E2%7D%2Bb%5E2%29%7D%7D)
![dL/db=\frac{2b-2048\cdot b^{-3}}{2\sqrt{(\frac{1024}{b^2}+b^2)}}=0\\\\\\2b-2048b^{-3}=0\\\\2b=\frac{2048}{b^3}\\\\b^4=\frac{2048}{2} =1024\\\\b=\sqrt[5]{1024}\approx5.66](https://tex.z-dn.net/?f=dL%2Fdb%3D%5Cfrac%7B2b-2048%5Ccdot%20b%5E%7B-3%7D%7D%7B2%5Csqrt%7B%28%5Cfrac%7B1024%7D%7Bb%5E2%7D%2Bb%5E2%29%7D%7D%3D0%5C%5C%5C%5C%5C%5C2b-2048b%5E%7B-3%7D%3D0%5C%5C%5C%5C2b%3D%5Cfrac%7B2048%7D%7Bb%5E3%7D%5C%5C%5C%5Cb%5E4%3D%5Cfrac%7B2048%7D%7B2%7D%20%20%3D1024%5C%5C%5C%5Cb%3D%5Csqrt%5B5%5D%7B1024%7D%5Capprox5.66)
Now, we know that one side is 5.66 cm.
Then, the other side should be:

The length of the line for this side dimensions will be:
