In the anion `HCOO^(-)`, the two carbon-oxygen bonds are found to be equal length. What is the reason for it?

In the anion HCOO^(-) , the two carbon-oxygen bonds are found to be of equal length. What is the reason for it ?

In an anion HCOO^- the two carbon-oxygen bonds are found to be equal length. What is the reason for it?

In the HCOO^- the two carbon-oxygen bonds are found to be of equal length. What is the reason for it ?