Title: Isosceles triangle
Content: is acute, right or obtuse depends only on the angle at its apex. In Euclidean geometry, the base angles cannot be obtuse (greater than 90°) or right (equal to 90°) because their measures would sum to at least 180°, the total of all angles in any Euclidean triangle. Since a triangle is obtuse or right if and only if one of its angles is obtuse or right, respectively, an isosceles triangle is obtuse, right or acute if and only if its apex angle is respectively obtuse, right or acute. In Edwin Abbott's book "Flatland", this classification of shapes was used

Title: Rights
Content: angle"), "straight" and "stretch". Like "right", the English words "rule" and "ruler", deriving still from the same root, have both normative or regulatory and geometric meanings (e.g. a ruler as in a king, or a ruler as in a straightedge). Several other roots have similar normative and geometric descendants, such as Latin "norma", whence "norm", "normal", and "normative" itself, and also geometric concepts such as "normal vectors"; and likewise Greek "ortho" and Latin "ordo", meaning either "right" or "correct" (as in "orthodox", meaning "correct opinion") or "straight" or "perpendicular" (as in "orthogonal", meaning "perpendicular angle"), and thence "order", "ordinary", etc.

Title: Angle
Content: deviation from a straight line; the second by Carpus of Antioch, who regarded it as the interval or space between the intersecting lines; Euclid adopted the third concept, although his definitions of right, acute, and obtuse angles are certainly quantitative. In mathematical expressions, it is common to use Greek letters (α, β, γ, θ, φ, . . . ) to serve as variables standing for the size of some angle. (To avoid confusion with its other meaning, the symbol is typically not used for this purpose.) Lower case Roman letters ("a", "b", "c", . . . ) are also used,

Title: Right angle
Content: of what a right angle is, namely two straight lines intersecting to form two equal and adjacent angles. The straight lines which form right angles are called perpendicular. Euclid uses right angles in definitions 11 and 12 to define acute angles (those smaller than a right angle) and obtuse angles (those greater than a right angle). Two angles are called complementary if their sum is a right angle. Book 1 Postulate 4 states that all right angles are equal, which allows Euclid to use a right angle as a unit to measure other angles with. Euclid's commentator Proclus gave a

Title: Laterality
Content: word "lyft" which means "weak" or "useless". Similarly, the French word for left, "gauche", is also used to mean "awkward" or "tactless", and "sinistra", the Latin word from which the English word "sinister" was derived, means "left". Similarly, in many cultures the word for "right" also means "correct". The English word "right" comes from the Anglo-Saxon word "riht" which also means "straight" or "correct." This linguistic and social bias is not restricted to European cultures: for example, Chinese characters are designed for right-handers to write, and no significant left-handed culture has ever been found in the world. When a person

Question: What are classified by their measurement in degrees as "right", "reflex", "obtuse", or "acute"?
Answer: Angles