Détendre is a french third group verb. So, this verb is irregular and do not follow a regular conjugation pattern like first or second group verbs. Follow this link to see all the endings of the conjugation of most of the third group verbs :
conjugation rules and endings for the second group verbs.
Most verbs in
-dre:
-andre, -endre, -ondre, -erdre, -ordre conjugate like
rendre (major exceptions are those in
-indre and
-oudre).
Prendre and its compounds, however, have a very different conjugation, where the
d is only kept in the future and conditional.
Détendre verb is conjugated in female form and in reflexive form. Be careful, the past participle of compound tenses must agree with the subject.
Détendre verb is conjugated in interrogative form. For sound reasons, an euphonious
« t » is added to the pronoun of the third person:
« il »,
« elle »,
« on »,
« ils »,
« elles » except when the verb ends with
« t » or
« d »:
« détendra-t-elle ? »,
« a-t-elle détendu ? »,
« aura-t-elle détendu ? ».
Finally, the interrogative form does not exist in subjunctive and imperative.