Question

where the use of has to and have to

Answer 1

has to is used when there is singularity .

have to is used when there is plurality.

but both of them are used to refer present situations..

bests seldon

Answer 2

 where is compulsion to do any work.then use 'have to' and 'has to'.
ex. I have to finish the works because I have not any other way.