Approximations of πApproximations for the mathematical constant pi (pi) in the history of mathematics reached an accuracy within 0.04% of the true value before the beginning of the Common Era. In Chinese mathematics, this was improved to approximations correct to what corresponds to about seven decimal digits by the 5th century. Further progress was not made until the 15th century (through the efforts of Jamshīd al-Kāshī).
X3DX3D (Extensible 3D) is a set of royalty-free ISO/IEC standards for declaratively representing 3D computer graphics. X3D includes multiple graphics file formats, programming-language API definitions, and run-time specifications for both delivery and integration of interactive network-capable 3D data. X3D version 4.0 has been approved by Web3D Consortium, and is under final review by ISO/IEC as a revised International Standard (IS). X3D is specifically designed to work across diverse devices by using the Web Architecture.
Back painBack pain is pain felt in the back. It may be classified as neck pain (cervical), middle back pain (thoracic), lower back pain (lumbar) or coccydynia (tailbone or sacral pain) based on the segment affected. The lumbar area is the most common area affected. An episode of back pain may be acute, subacute or chronic depending on the duration. The pain may be characterized as a dull ache, shooting or piercing pain or a burning sensation. Discomfort can radiate to the arms and hands as well as the legs or feet, and may include numbness or weakness in the legs and arms.
4X4X (abbreviation of Explore, Expand, Exploit, Exterminate) is a subgenre of strategy-based computer and board games, and includes both turn-based and real-time strategy titles. The gameplay generally involves building an empire. Emphasis is placed upon economic and technological development, as well as a range of military and non-military routes to supremacy. The earliest 4X games borrowed ideas from board games and 1970s text-based computer games. The first 4X computer games were turn-based, but real-time 4X games are common.
