Human penis tension of the suspensory ligament that holds it in position. The following table shows how common various erection angles are for a standing male, out of a sample of 1,564 males aged 20 through 69. In the table, zero degrees is pointing straight up against the abdomen, 90 degrees is horizontal and pointing straight forward, while 180 degrees would be pointing straight down to the feet. An upward pointing angle is most common. Ejaculation is the ejecting of semen from the penis, and is usually accompanied by orgasm. A series of muscular contractions delivers semen, containing male gametes known as
Angle trisection and the mark on the line is labeled . This ensures that . A radius is drawn to make it obvious that line segments , , and all have equal length. Now, triangles and are isosceles, thus (by Fact 3 above) each has two equal angles. Hypothesis: Given is a straight line, and , , and all have equal length, Conclusion: angle . Proof: Clearing, , or , and the theorem is proved. Again, this construction stepped outside the framework of allowed constructions by using a marked straightedge. Thomas Hutcheson published an article in the Mathematics Teacher that used a