When you supplicate and call Allah with His names, you remove the definite article “Al” and you Say “Ya Rahman, Ya Haleem”. With Allah, you say Ya Allah.

I would like to used the 99 names of Allah in my dua, but different names at different times. confused as to how i say them (pronounce) when i am saying this in dua (with the right start e.g. Ar), and i am worried about saying this wrong. I know that for Rahman, it is said as Ar-Rahman, when i say this in dua.