Angelfish don't typically show any significant sexual dimorphism. It's hard to tell sexes without seeing the genital papilla, the tube that the fish extends to deposit milt or eggs (also called the ovipositor in females). A male's is narrow and pointed, while a female's is bigger around and blunt. I don't see any signs of either in your fish.
Some cichlids can be "vented", turning the fish over and looking at the shape, size and/or color of the genital pore to determine sex. Angelfish are not one of these cichlids. So if someone tells you that you can vent your angelfish, don't. It will cause stress to your fish with no benefit. Venting is very effective with Rift Valley cichlids, I've vented hundreds. But a majority of New World species can't be vented with any measure of reliability. With many Central and South American cichlids, however, it doesn't matter. Sub-adults and adults show sexual dimorphism (differences in size, color intensity, shape of fins, presence of a nuchal hump in males, etc.). Unfortunately, angelfish are a species that shows no significant, reliable differences between males and females externally, except for the genital papilla during breeding.
For future reference, if you're interested, oscars are another species that can't be vented and show no significant difference in the appearance of the sexes.
WYite