Angelfish can only be accurately sexed using their breeding tubes. Those are located night near where the poop comes out. Are you able to see anything there?
There are certain traits that are more common in one gender over the other, but even those can't be seen with the photo you have given. We would need to see a good side profile shot to even venture a guess.
But again, the breeding tube is the only accurate way. I have had plenty of angels surprise me.
I was able to see something really realy small. but these angelfish are 6-7 months in my aquarium and when I got them they were around 2 months old (3-4 cm) now they are around 8-10 cm.
The black one seemed to be male and the white female, but I believe they are too small for me to be sure.
Reason why I asked is because in the aquarium I have 3 angelfish. 1 of them has been left out, the other 2 seemed to be paired up and became a bit more agressive then they used to, including with the other angel fish.