In geometry , the midpoint is the middle point of a line segment . It is equidistant from both endpoints, and it is the centroid both of the segment and of the endpoints. It bisects the segment.
19-668: The Shell Rock River is a 113-mile-long (182 km) tributary of the West Fork Cedar River in southern Minnesota and northern Iowa in the United States . Via the Cedar and Iowa rivers, it is part of the Mississippi River watershed . This river was named for the fossil shells found in outcroppings along its banks. The United States Board on Geographic Names settled on "Shell Rock River" as
38-440: A 1 , a 2 , … , a n ) {\displaystyle A=(a_{1},a_{2},\dots ,a_{n})} and B = ( b 1 , b 2 , … , b n ) {\displaystyle B=(b_{1},b_{2},\dots ,b_{n})} is given by That is, the i coordinate of the midpoint ( i = 1, 2, ..., n ) is Given two points of interest, finding
57-400: A new river, to be given its own name, perhaps one already known to the people who live upon its banks. Conversely, explorers approaching a new land from the sea encounter its rivers at their mouths, where they name them on their charts, then, following a river upstream, encounter each tributary as a forking of the stream to the right and to the left, which then appear on their charts as such; or
76-400: A river or stream that branches off from and flows away from the main stream. Distributaries are most often found in river deltas . Right tributary , or right-bank tributary , and left tributary , or left-bank tributary , describe the orientation of the tributary relative to the flow of the main stem river. These terms are defined from the perspective of looking downstream, that is, facing
95-449: Is a stream or river that flows into a larger stream ( main stem or "parent" ), river, or a lake . A tributary does not flow directly into a sea or ocean . Tributaries, and the main stem river into which they flow, drain the surrounding drainage basin of its surface water and groundwater , leading the water out into an ocean. The Irtysh is a chief tributary of the Ob river and
114-411: Is also the longest tributary river in the world with a length of 4,248 km (2,640 mi). The Madeira River is the largest tributary river by volume in the world with an average discharge of 31,200 m /s (1.1 million cu ft/s). A confluence , where two or more bodies of water meet, usually refers to the joining of tributaries. The opposite to a tributary is a distributary ,
133-420: Is not naturally defined in projective geometry since there is no distinguished point to play the role of the point at infinity (any point in a projective range may be projectively mapped to any other point in (the same or some other) projective range). However, fixing a point at infinity defines an affine structure on the projective line in question and the above definition can be applied. The definition of
152-421: The direction the water current of the main stem is going. In a navigational context, if one were floating on a raft or other vessel in the main stream, this would be the side the tributary enters from as one floats past; alternately, if one were floating down the tributary, the main stream meets it on the opposite bank of the tributary. This information may be used to avoid turbulent water by moving towards
171-453: The first-order tributary being typically the least in size. For example, a second-order tributary would be the result of two or more first-order tributaries combining to form the second-order tributary. Another method is to list tributaries from mouth to source, in the form of a tree structure , stored as a tree data structure . Midpoint The midpoint of a segment in n -dimensional space whose endpoints are A = (
190-451: The handedness is from the point of view of an observer facing upstream. For instance, Steer Creek has a left tributary which is called Right Fork Steer Creek. These naming conventions are reflective of the circumstances of a particular river's identification and charting: people living along the banks of a river, with a name known to them, may then float down the river in exploration, and each tributary joining it as they pass by appears as
209-485: The line connecting the cusps intersects the segment is then the midpoint of the segment. It is more challenging to locate the midpoint using only a compass, but it is still possible according to the Mohr-Mascheroni theorem . The abovementioned formulas for the midpoint of a segment implicitly use the lengths of segments. However, in the generalization to affine geometry , where segment lengths are not defined,
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#1732776141428228-408: The midpoint can still be defined since it is an affine invariant . The synthetic affine definition of the midpoint M of a segment AB is the projective harmonic conjugate of the point at infinity , P , of the line AB . That is, the point M such that H[ A , B ; P , M ] . When coordinates can be introduced in an affine geometry, the two definitions of midpoint will coincide. The midpoint
247-402: The midpoint of the line segment they determine can be accomplished by a compass and straightedge construction . The midpoint of a line segment, embedded in a plane , can be located by first constructing a lens using circular arcs of equal (and large enough) radii centered at the two endpoints, then connecting the cusps of the lens (the two points where the arcs intersect). The point where
266-469: The opposite bank before approaching the confluence. An early tributary is a tributary that joins the main stem river closer to its source than its mouth, that is, before the river's midpoint ; a late tributary joins the main stem further downstream, closer to its mouth than to its source, that is, after the midpoint. In the United States, where tributaries sometimes have the same name as
285-666: The river into which they feed, they are called forks . These are typically designated by compass direction. For example, the American River in California receives flow from its North, Middle, and South forks. The Chicago River 's North Branch has the East, West, and Middle Fork; the South Branch has its South Fork, and used to have a West Fork as well (now filled in). Forks are sometimes designated as right or left. Here,
304-418: The smaller stream designated the little fork, the larger either retaining its name unmodified, or receives the designation big . Tributaries are sometimes listed starting with those nearest to the source of the river and ending with those nearest to the mouth of the river . The Strahler stream order examines the arrangement of tributaries in a hierarchy of first, second, third and higher orders, with
323-601: The stream's name in 1931. According to the Geographic Names Information System , it has also been known by the spelling "Shellrock River". The Shell Rock River flows from Albert Lea Lake in Freeborn County, Minnesota , and soon enters Iowa, flowing generally south-southeastwardly through eastern Worth , northeastern Cerro Gordo , western Floyd , northeastern Butler , southwestern Bremer and northwestern Black Hawk counties, past
342-432: The streams are seen to diverge by the cardinal direction (north, south, east, or west) in which they proceed upstream, sometimes a third stream entering between two others is designated the middle fork; or the streams are distinguished by the relative height of one to the other, as one stream descending over a cataract into another becomes the upper fork, and the one it descends into, the lower ; or by relative volume:
361-795: The town of Glenville in Minnesota and the towns of Northwood , Plymouth , Rock Falls , Nora Springs , Rockford , Marble Rock , Greene , Clarksville and Shell Rock in Iowa. It joins the West Fork of the Cedar River in Black Hawk County, about 6 miles (10 km) north-northwest of Cedar Falls . At Rockford, Iowa, it collects the Winnebago River from the west. Tributary A tributary , or an affluent ,
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