- In geometry and trigonometry, a right angle is an angle of exactly 90 degrees or đ/2 radians 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.
- Alkaid (stars.astro.illinois.edu)
ALKAID (Eta Ursae Majoris). Though the name may not be so well known as those of the first magnitude stars, the star itself certainly is, as Alkaid is the end star in the handle of the Big Dipper, the great asterism that makes most of the grand constellation of Ursa Major, the Greater Bear.
