The matter torments representatives of a strong half of mankind more today. When the man sees that his darling has a friend, of course, at once there is a small mistrust to the girlfriend and a jealousy drop therefore let's understand this question.
To trust each other and representatives of different floors can communicate at the level of the Platonic relations until between them there is no physical inclination to each other, that is desires to have sex. If such inclination unilateral, then, most likely, one of partners suffers, loving the friend or the girlfriend and it is already impossible to call it friendship. Before puberty the representatives of different floors without problems can be on friendly terms with each other, but with approach of puberty even if both will have other love relations, the experiences concerning the choice, most likely, the guy with the girl - friends will share with each other, than with the elects. From there is a jealousy and quarrels. At a difficult moment - the parting period, or quarrels with darling the support of the friend is very important, who can explain better an act of the beloved or woman, than the friend of the same floor? But between such friends always there has to be a small distance - purely Platonic relations. Of course, friendship between the man and the woman is possible even if they have sex by agreement only as satisfaction of physical requirements. But often such relations occur when both have no permanent partners.
Friendship between the man and the woman is impossible?
The majority inclines to opinion that this is true, for the reason, that such relations can develop into something bigger sooner or later - offenses, quarrels not only between friends, but also can significantly spoil love, both the man, and the woman. For this reason friendship can exist between the former lovers, spouses, or to be limited to rare communication.