must ascertain
Verbe régulier : ascertain - ascertained- ascertained
Traduction française : établir - constater 

Affirmation 	
Forme simple 	Forme en V-ing 	Perfect 	Perfect en V-ing 	
I must ascertain
you must ascertain
he must ascertain
we must ascertain
you must ascertain
they must ascertain 	I must be ascertaining
you must be ascertaining
he must be ascertaining
we must be ascertaining
you must be ascertaining
they must be ascertaining	I must have ascertained
you must have ascertained
he must have ascertained
we must have ascertained
you must have ascertained
they must have ascertained	I must have been ascertaining
you must have been ascertaining
he must have been ascertaining
we must have been ascertaining
you must have been ascertaining
they must have been ascertaining	

Négation 	
Forme simple 	Forme en V-ing 	Perfect 	Perfect en V-ing 	
I must not ascertain
you must not ascertain
he must not ascertain
we must not ascertain
you must not ascertain
they must not ascertain 	I must not be ascertaining
you must not be ascertaining
he must not be ascertaining
we must not be ascertaining
you must not be ascertaining
they must not be ascertaining	I must not have ascertained
you must not have ascertained
he must not have ascertained
we must not have ascertained
you must not have ascertained
they must not have ascertained	I must not have been ascertaining
you must not have been ascertaining
he must not have been ascertaining
we must not have been ascertaining
you must not have been ascertaining
they must not have been ascertaining	

Forme interrogative 	
Forme simple 	Forme en V-ing 	Perfect 	Perfect en V-ing 	
must I ascertain?
must you ascertain?
must he ascertain?
must we ascertain?
must you ascertain?
must they ascertain? 	must I be ascertaining?
must you be ascertaining?
must he be ascertaining?
must we be ascertaining?
must you be ascertaining?
must they be ascertaining? 	must I have ascertained?
must you have ascertained?
must he have ascertained?
must we have ascertained?
must you have ascertained?
must they have ascertained? 	must I have been ascertaining?
must you have been ascertaining?
must he have been ascertaining?
must we have been ascertaining?
must you have been ascertaining?
must they have been ascertaining? 	

Forme interro-négative 	
Forme simple 	Forme en V-ing 	Perfect 	Perfect en V-ing 	
must I not ascertain?
must you not ascertain?
must he not ascertain?
must we not ascertain?
must you not ascertain?
must they not ascertain? 	must I not be ascertaining?
must you not be ascertaining?
must he not be ascertaining?
must we not be ascertaining?
must you not be ascertaining?
must they not be ascertaining? 	must I not have ascertained?
must you not have ascertained?
must he not have ascertained?
must we not have ascertained?
must you not have ascertained?
must they not have ascertained? 	must I not have been ascertaining?
must you not have been ascertaining?
must he not have been ascertaining?
must we not have been ascertaining?
must you not have been ascertaining?
must they not have been ascertaining?