Effective resistance between A and B:
Resistance along AFE: 4 ohms.
it is in parallel with 4 ohms along AE. Hence, effective resistance of these two:
= 4 * 4 /(4+4) = 2 ohms
resistance along AED: 2 ohms + 2 ohms = 4 ohms.
This is in parallel with the resistance along AD : 4 ohms.
Hence the effective resistance : 2 ohms .
This is in series with resistance 2 ohms along CD. HEnce, total resistance along ADC is 4 ohms.
This is parallel with the 4 ohms resistance along AC. Effective resistance then is 2 ohms. This is in series with 2 ohms along BC.
Hence the along ACB the resistance is 4 ohms.
Between A and B there are two 4 ohms resistances in parallel.
Hence, effective resistance between A and B = 2 ohms.
effective resistance between A and D:
Total resistance along ABC = 6 ohms.
Between A and C we have 4 ohms and 6 ohms in parallel.
equivalent Resistance between A & C along AC: 6*4/(6+4) = 2.4 ohms
Add this to the resistance 2 ohms between C and D. Hence, Along ACD the resistance is 4.4 ohms.
similarly, on the other side, Equivalent resistance along AED will be 4.4 ohms, from symmetry.
Now, 4 ohms between A and D, 4.4 ohms along AED, and 4.4 ohms along ACD are all in parallel.
equivalent resistance along AD: R (say).
1/ R = 1/4 + 1/4.4 + 1/4.4 = (1.1 +1+1)/4.4 = 3.1/4.4
R = 4.4 / 3.1 ohms = 1.42 ohms.