The side lengths of a right triangle form a so-called Pythagorean triple. A triangle that is not a right triangle is sometimes called an oblique triangle. Special cases of the right triangle include the isosceles right triangle (middle figure) and 30-60-90 triangle (right figure).
The first pacemaker was implanted on 8th October 1958 in a 43 year old man called Arne Larsson with complete heart block and Stokes-Adams attacks. Technological innovations between 1973 and 1980 rendered obsolete the reliable pacemaker of 1970.
The history of protective respiratory equipment can be traced back as far as the first century, when Pliny the Elder (circa A.D. 23-79) described using animal bladder skins to protect workers in Roman mines from red lead oxide dust.