Merkle Root for 1-transaction block! I know that merkle hash for one transaction tx is:

sha256(sha256(tx))

In this block:
https://blockchain.info/block/000000000000000001291219dde8ed705903e8c101f416c68a439e5171ede5bc

there is only one transaction, but the merkle root equals to transaction hash!!!

So, how merkle root can be calculated???
The merkle root of a block is the hash of all of the transactions. If there is one transaction, then the hash of all of the transactions is the hash of that one transaction. So the merkle root and the txid of the only transaction in a one transaction block will be the same.