Right angle Right angle In geometry and trigonometry, a right angle is an angle of exactly 90° (degrees), corresponding to a quarter turn. If a ray is placed so that its endpoint is on a line and the adjacent angles are equal, then they are right angles. The term is a calque of Latin "angulus rectus"; here "rectus" means "upright", referring to the vertical perpendicular to a horizontal base line. Closely related and important geometrical concepts are perpendicular lines, meaning lines that form right angles at their point of intersection, and orthogonality, which is the property of forming right angles, usually applied
61 cm Type 90 torpedo 61 cm Type 90 torpedo The 61 cm Type 90 torpedo was a surface-fired torpedo used by the Imperial Japanese Navy during World War II. It was used in the s and in most cruisers, including the , , , and heavy cruisers after refits during the 1930s. It was superseded by the Type 93 oxygen-powered torpedo, commonly called the "Long Lance", as oxygen generating equipment was installed aboard the cruisers. The torpedo was based on a newly developed British Whitehead torpedo. This weapon used a new double-action two-cylinder engine rather than the four-cylinder radial engine used by World War