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.
The 20th Century. Average Age: 12-13. In 1928, Howard Kelly, a gynecology professor at John Hopkins University, claimed that the average age to get your period for American girls was 13.9. Surveys of British teens in the 1950s and '60s found that they typically got their first period around 13.5 years of age.