Final answer:
Cyrano chooses not to reveal his love to Roxane after Christian's death out of respect because for both Christian's memory and Roxane's mourning, ultimately sacrificing his own feelings to preserve the love Roxane had for Christian based on the letters Cyrano wrote.
Step-by-step explanation:
Once Christian dies, Cyrano realizes that he cannot tell Roxane of his love because he honors Christian's memory and respects Roxane's grief. He also believes that Roxane truly loved Christian for his handsome appearance and the soul he thought was revealed through the letters, which Cyrano himself wrote.
Therefore, Cyrano chooses to keep his authorship of the letters and his own love for Roxane a secret, to preserve the image of Christian that Roxane cherishes. This theme of unrequited and sacrificial love is a central motif in the play 'Cyrano de Bergerac' by Edmond Rostand.