explain the triangle between higgins eliza and dolittle and how does it change by the end of the play?provide examples

I'm not sure what you mean by triangle, love triangle? A love triangle isn't possible; we have Eliza, her father, and Henry listed above. A love triangle might include Freddy, but you haven't referenced him in your question. Any kind of triangle that would have existed between the three individuals you cite would have to be relational. Both Henry and Eliza's father use her for their own purposes; Henry uses Eliza as an experiment; her father uses her as a source of money. Neither man deserves her loyalty or love, but they both mean everything to her. In the end, her father moves on and tells her he's getting married (doesn't need her anymore), and Henry eventually figures out her true worth, but she sends him away.