Примеры использования Convex quadrilateral на Английском языке и их переводы на Русский язык
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The two bimedians of a convex quadrilateral are the line segments that connect the midpoints of opposite sides.
Can one draw three triangles so that both their intersection andtheir union are convex quadrilaterals?
A convex quadrilateral is ex-tangential if and only if there are six concurrent angles bisectors.
The Newton line is the line that connects the midpoints of the two diagonals in a convex quadrilateral that is not a parallelogram.
A convex quadrilateral is equidiagonal if and only if its Varignon parallelogram, the parallelogram formed by the midpoints of its sides, is a rhombus.
The line segments connecting the midpoints of opposite sides of a convex quadrilateral intersect in a point that lies on the Newton line.
A convex quadrilateral is orthodiagonal if and only if its Varignon parallelogram(whose vertices are the midpoints of its sides) is a rectangle.
In Euclidean geometry, an equidiagonal quadrilateral is a convex quadrilateral whose two diagonals have equal length.
There are several metric characterizations regarding the four triangles formed by the diagonal intersection P and the vertices of a convex quadrilateral ABCD.
The converse is also true: a circle can be inscribed into every convex quadrilateral in which the lengths of opposite sides sum to the same value.
Conversely, a convex quadrilateral in which the four angle bisectors meet at a point must be tangential and the common point is the incenter.
In particular, the rectilinear crossing number of a complete graph is essentially the same as the minimum number of convex quadrilaterals determined by a set of n points in general position.
Otherwise, the four points form a convex quadrilateral and the geometric median is the crossing point of the diagonals of the quadrilateral. .
If rectangles are included in the class of trapezoids then one may concisely define an isosceles trapezoid as"a cyclic quadrilateral with equal diagonals" oras"a cyclic quadrilateral with a pair of parallel sides" or as"a convex quadrilateral with a line of symmetry through the mid-points of opposite sides.
Convex quadrilaterals whose side lengths form an arithmetic progression are always ex-tangential as they satisfy the characterization below for adjacent side lengths.
In the nonoverlapping triangles APB, BPC, CPD,DPA formed by the diagonals in a convex quadrilateral ABCD, where the diagonals intersect at P, there are the following characterizations of tangential quadrilaterals. .
Thus a convex quadrilateral has an incircle or an excircle outside the appropriate vertex(depending on the column) if and only if any one of the five necessary and sufficient conditions below is satisfied.
A quadrilateral is equidiagonal if and only if K m n.{\displaystyle\displaystyle K=mn.}This is a direct consequence of the fact that the area of a convex quadrilateral is twice the area of its Varignon parallelogram and that the diagonals in this parallelogram are the bimedians of the quadrilateral. .
The diagonals of a convex quadrilateral ABCD are perpendicular if and only if∠ P A B+∠ P B A+∠ P C D+∠ P D C π{\displaystyle\angle PAB+\angle PBA+\angle PCD+\angle PDC=\pi} where P is the point of intersection of the diagonals.
According to the Pitot theorem, the two pairs of opposite sides in a tangential quadrilateral add up to the same total length, which equals the semiperimeter s of the quadrilateral: a+ c b+ d a+ b+ c+ d 2 s.{\displaystyle a+c=b+d={\frac{ a+b+c+d}{ 2}}= s.}Conversely a convex quadrilateral in which a+ c b+ d must be tangential.
Another necessary andsufficient condition is that a convex quadrilateral ABCD is tangential if and only if the incircles in the two triangles ABC and ADC are tangent to each other.
If opposite sides in a convex quadrilateral ABCD intersect at E and F, then A B+ B C A D+ D C⇔ A E+ E C A F+ F C.{\displaystyle AB+BC=AD+DC\quad\Leftrightarrow\quad AE+EC=AF+FC.} The implication to the right is named after L. M. Urquhart(1902-1966) although it was proved long before by Augustus De Morgan in 1841.
In fact the converse also holds: given two circles(one within the other) with radii R and r and distance x between their centers satisfying the condition in Fuss' theorem,there exists a convex quadrilateral inscribed in one of them and tangent to the other and then by Poncelet's closure theorem, there exist infinitely many of them.
Another necessary and sufficient condition for a convex quadrilateral ABCD to be cyclic is that an angle between a side and a diagonal is equal to the angle between the opposite side and the other diagonal.
A convex quadrilateral with diagonal lengths p{\displaystyle p} and q{\displaystyle q} and bimedian lengths m{\displaystyle m} and n{\displaystyle n} is equidiagonal if and only if p q m 2+ n 2.{\displaystyle pq= m^{ 2}+ n^{ 2}.} The area K of an equidiagonal quadrilateral can easily be calculated if the length of the bimedians m and n are known.
From this equation it follows almost immediately that the diagonals of a convex quadrilateral are perpendicular if and only if the projections of the diagonal intersection onto the sides of the quadrilateral are the vertices of a cyclic quadrilateral. .
If opposite sides in a convex quadrilateral ABCD(that is not a trapezoid) intersect at E and F, then it is tangential if and only if either of B E+ B F D E+ D F{\displaystyle\displaystyle BE+BF=DE+DF} or A E- E C A F- F C.{\displaystyle\displaystyle AE-EC=AF-FC.} The second of these is almost the same as one of the equalities in Urquhart's theorem.
It states that when a convex quadrilateral is divided into four nonoverlapping triangles by its two diagonals, then the incenters of the four triangles are concyclic if and only if the quadrilateral is tangential.
If the normals to the sides of a convex quadrilateral ABCD through the diagonal intersection intersect the opposite sides in R, S, T, U, and K, L, M, N are the feet of these normals, then ABCD is orthodiagonal if and only if the eight points K, L, M, N, R, S, T and U are concyclic; the second eight point circle.
A quadrilateral is called convex if both its diagonals pass inside it.