An example of modern architecture, designed with many right angles.

In geometry and trigonometry, a right angle is defined as an angle between two straight intersecting lines of ninety degrees, or one-quarter of a circle. Right angles are perpendicular, and have important properties in mathematics. The presence of a right angle in a triangle is the defining factor for right triangles. Image File history File links Right_angle. ... Image File history File links Right_angle. ... Image File history File links Metadata No higher resolution available. ... Image File history File links Metadata No higher resolution available. ... Calabi-Yau manifold Geometry (Greek γεωμετρία; geo = earth, metria = measure) is a part of mathematics concerned with questions of size, shape, and relative position of figures and with properties of space. ... Wikibooks has a book on the topic of Trigonometry All of the trigonometric functions of an angle θ can be constructed geometrically in terms of a unit circle centered at O. Trigonometry (from Greek trigōnon triangle + metron measure[1]), informally called trig, is a branch of mathematics that deals with... ∠, the angle symbol. ... Look up line in Wiktionary, the free dictionary. ... Circle illustration This article is about the shape and mathematical concept of circle. ... Fig. ... Euclid, Greek mathematician, 3rd century BC, as imagined by by Raphael in this detail from The School of Athens. ... A triangle. ... For alternate meanings, such as the musical instrument, see triangle (disambiguation). ...

A right angle may be expressed in different units:

• 90°
• When a straight line standing on a straight line makes the adjacent angles equal to one another, each of the equal angles is right—in Euclid's Elements
• full circle
• rad
• Babylonian unit
• 100 grad (also called grade, gradian, or gon)
• 8 points (of a compass rose)
• 6 hours (astronomical hour angle)
• The angle of perpendicularity
• ∞% grade on the tangent scale
• 100% grade on the sine scale.

fgeryfuywvhbvwrhjoooodcjdjns cbcebfceedwdjdjdjdenhedbbedbhjefdhjnefwku/;bgifRWBGEKDMNECDBHUJEWKJUL;Bhn/'inorgvwh3earsjndflvr'[['{"[tbptf rgwenvreankbfknvfendvfnkdfv efrdv ver evrf evfr vefrdergbv rgvfefgtvr nhtkbgrl,intrefngveklrdnfv erdfnglbgtrfgnhjgebjngernjgrn rglnkergngrwnklerlnrgejergjlergjlrgejerggerknger gerklgerlkgrwklnjegrlnkergnklgerlnkgrgnlkgerlngern frg ger rge reg erg ergewgr,mgrljbnrhgeouu?:PODCker4wjif8kAM8fero;,{"OP:lgjn4;o4jgeje4wasj;awoes^{Superscript text} The grad is a measurement of plane angles of value 1/400 of a full circle, thus dividing a right angle in 100. ... A common compass rose as is found on a nautical chart showing both true and magnetic north with magnetic declination A compass rose is a figure displaying the orientation of the cardinal directions, north, south, east and west on a map or nautical chart. ... In astronomy, an objects hour angle (HA) is defined as the difference between the current local sidereal time (LST) and the right ascension () of the object: HAobject = LST - object Thus, the objects hour angle indicates how much sidereal time has passed since the object was on the local... Fig. ... A grade (or gradient) is the pitch of a slope, and is often expressed as a percent tangent, or rise over run. It is used to express the steepness of slope on a hill, roof, or road, where zero indicates level (with respect to gravity) and increasing numbers correlate to...