In Euclidean geometry the sum of the angles of a triangle is equal to two right angles (180Â°). If all three angles of a triangle are equal, the triangle is called equilateral. An isosceles triangle has two equal angles. A scalene triangle is one in which all three angles are different.
A period, or menstruation, is the shedding of the endometrium-the uterine lining. Menstruation is also known as menses. All female humans, as well as some other female mammals, have regular periods during their reproductive age. Menstruation which includes bleeding from the vagina is found mainly among humans and similar animals, such as primates.
On average, most girls start their periods when they're 12 or 13 years old (although some begin earlier or later). But if you wait until your daughter gets her period to talk to her about menstruation, that's too late.