cosigné

In a sentence

• J'ai cosigné l'accord avec mon partenaire de projet.

  I co-signed the agreement with my project partner.

  The word "cosigné" is used here as a past participle to indicate that the subject (I) shared the signing responsibility of the agreement.

• Elle m'a demandé de cosigner le document important.

  She asked me to co-sign the important document.

  In this sentence, "cosigner" is the infinitive form of the verb, showing the action of sharing the signing responsibility.

• Nous avons cosigné plusieurs lettres adressées à la direction.

  We co-signed several letters addressed to the management.

  Here, "cosigné" is again the past participle, indicating that a group shared the responsibility of signing multiple letters.