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
How Are We to Live? How Are We to Live? How Are We to Live?: Ethics in an Age of Self-Interest is a book on applied ethics by bioethical philosopher Peter Singer. It was first published in 1993, with subsequent editions in later years. Singer argues that doing the right thing involves attending to the sufferings and preferences of other sentient beings. Singer presents a history of ethical thought, and attempts to refute the popular idea that humans are genetically driven to be selfish. He explains how this idea has been attributed to Thomas Hobbes and Adam Smith, and how politicians like Margaret Thatcher and