It is difficult to tell between the male and female angelfish. There are, however, subtle differences between the male and female angelfish. For instance, in the males, the head will be a more rounded head as compared to the females.
Another difference is the angle the dorsal fin makes with the head. Remember, the dorsal fin is the fin on top of the fish. In males, the angle is sharp about 120 to 130 degrees. In females, the angle is pretty straight about 180 degrees.
Another way of distinguishing is the outline of the body from the pectoral fins to the anal fin. In males, there is a distinct angle in the outline between the pectoral fins and the anal fins. In females, it is pretty much horizontal.
Another distinction is in the papilla formed when the fish are about to breed. The papilla is a hollow tubular projection. In females, this helps lay eggs while in males it helps fertilize them.
The papilla is round in females and thin and pointed in the males. Angel fish are easier to sex once they have attained sexual maturity. If you desire to breed angels, you can buy about six angels and the fish will form pairs by themselves.