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 menstrual cycle is from Day 1 of bleeding to Day 1 of the next time of bleeding. Although the average cycle is 28 days, it is normal to have a cycle that is shorter or longer. Girls usually start having menstrual periods between the ages of 11 and 14. Women usually start to have fewer periods between ages 39 and 51. Women in their 40s and teens may have cycles that are longer or change a lot.