could subtend
Regular verb: subtend - subtended- subtended

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could subtend
you could subtend
he could subtend
we could subtend
you could subtend
they could subtend 	I could be subtending
you could be subtending
he could be subtending
we could be subtending
you could be subtending
they could be subtending	I could have subtended
you could have subtended
he could have subtended
we could have subtended
you could have subtended
they could have subtended	I could have been subtending
you could have been subtending
he could have been subtending
we could have been subtending
you could have been subtending
they could have been subtending	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't subtend
you couldn't subtend
he couldn't subtend
we couldn't subtend
you couldn't subtend
they couldn't subtend 	I couldn't be subtending
you couldn't be subtending
he couldn't be subtending
we couldn't be subtending
you couldn't be subtending
they couldn't be subtending	I couldn't have subtended
you couldn't have subtended
he couldn't have subtended
we couldn't have subtended
you couldn't have subtended
they couldn't have subtended	I couldn't have been subtending
you couldn't have been subtending
he couldn't have been subtending
we couldn't have been subtending
you couldn't have been subtending
they couldn't have been subtending	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I subtend?
could you subtend?
could he subtend?
could we subtend?
could you subtend?
could they subtend? 	could I be subtending?
could you be subtending?
could he be subtending?
could we be subtending?
could you be subtending?
could they be subtending? 	could I have subtended?
could you have subtended?
could he have subtended?
could we have subtended?
could you have subtended?
could they have subtended? 	could I have been subtending?
could you have been subtending?
could he have been subtending?
could we have been subtending?
could you have been subtending?
could they have been subtending? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I subtend?
couldn't you subtend?
couldn't he subtend?
couldn't we subtend?
couldn't you subtend?
couldn't they subtend? 	couldn't I be subtending?
couldn't you be subtending?
couldn't he be subtending?
couldn't we be subtending?
couldn't you be subtending?
couldn't they be subtending? 	couldn't I have subtended?
couldn't you have subtended?
couldn't he have subtended?
couldn't we have subtended?
couldn't you have subtended?
couldn't they have subtended? 	couldn't I have been subtending?
couldn't you have been subtending?
couldn't he have been subtending?
couldn't we have been subtending?
couldn't you have been subtending?
couldn't they have been subtending?