Question

give scientific reasons
mango is an example for dicotyledonous plants

Answer 1

The best way to answer a question like this is to look up the information for yourself - very simple to google “mango” or “mango plant.” If the info isn’t given specifically, try something like “botanical classification for mango.” Probably the simplest and clearest info is on wikipedia, where the classification info is shown on a sidebar. If you still don’t see anything specific about monocot or dicot, look for more info on the clade or order - all plants within the same order are going to have the same cotyledon arrangement.