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
Angle grinder important factors in choosing the right grinder are the disc size and how powerful the motor is. Other factors include power source (pneumatic or electric), rpm, and arbor size. Generally disc size and power increase together. Disc size is usually measured in inches or millimetres. Common disc sizes for angle grinders in the United States include 4, 4.5, 5, 6, 7, 9 and 12 inches. Discs for pneumatic grinders also come much smaller. Pneumatic grinders are generally used for lighter duty jobs where more precision is required. This is likely because pneumatic grinders can be small and light yet remain