How to find the Bitcoin addresses used to create a Multi Signature address Assume we have a 2 of 3 multi signature address and we send some bitcoin to that address.

Then we spend the funds from that address by signing and broadcasting a transaction.

Just by looking at that transaction, can you tell the public keys whose private keys were used to sign that transaction?
Yes.

After the spending multisig transaction is on the blockchain (not the funding transaction), you can see the public keys used to spend those multisig funds.

These public keys are found in the full redeemScript provided in the spending transaction. See a breakdown of a multisig spending transaction here, which shows that a redeemScript is indeed included in the spending transaction. See a breakdown of the full redeemScript here, which shows that the public keys are included in this full redeemScript.

Let me clarify that the public keys are not seen in the funding transaction because only the redeemScript hash is revealed here, not the full redeem script.

Note: In the explanation above, I'm assuming you are talking about the Pay to Script Hash (P2SH) form of multisig, which is the more common and modern form of multisig. The answer to your question would still be yes for a non-P2SH multisig transaction, except that the public keys are visible in the funding transaction, rather than the spending transaction. The public keys are revealed in the scriptPubKey of the funding transaction, which looks like:

&lt;m&gt; &lt;A pubkey&gt; [B pubkey] [C pubkey...] &lt;n&gt; OP_CHECKMULTISIG


Source: https://bitcoin.org/en/developer-guide#multisig