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Suppose the diagonals meet at a point X.
AB is parallel to DC and BD intersects them
Therefore, angle ABD ( = ABX) = BAC (= BAX)
Therefore, in triangle ABX, the angles at the ends of AB are equal => the triangle is isosceles and so AX = BX.
AB is parallel to DC and AC intersects them
Therefore, angle ACD ( = XCD) = BDC (= XDC)
Therefore, in triangle CDX, the angles at the ends of CD are equal => the triangle is isosceles and so CX = DX.
Therefore AX + CX = BX + DX or, AC = BD.
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Show that if diagonals of a quadrilateral bisects each other then it is a rhombus?
This cannot be proven, because it is not generally true. If the diagonals of a quadrilateral bisect each other, then it is a parallelogram. And conversely, the diagonals of any parallelogram bisect each other. However not every parallelogram is a rhombus.However, if the diagonals are perpendicular bisectors, then we have a rhombus.Consider quadrilateral ABCD, with diagonals intersecting at X, whereAC and BD are perpendicular;AX=XC;BX=XD.Then angles AXB, BXC, CXD, DXA are all right angles and are congruent.By the ASA theorem, triangles AXB, BXC, CXD and DXA are all congruent.This means that AB=BC=CD=DA.Since the sides of the quadrilateral ABCD are congruent, it is a rhombus.
How do you prove that the diagonals and either base of an isosceles trapezoid form an isosceles triangle?
Consider the isosceles trapezium ABCD (going clockwise from top left) with AB parallel to CD. And let the diagonals intersect at O Since it is isosceles, AD = BC and <ADC = <BCD (the angles at the base BC). Now consider triangles ADC and BCD. AD = BC The side BC is common and the included angles are equal. So the two triangles are congruent. and therefore <ACD = <BDC Then, in triangle ODC, <OCD (=<ACD = <BDC) = <ODC ie ODC is an isosceles triangle. The triangle formed at the other base can be proven similarly, or by the fact that, because AB CD and the diagonals act as transversals, you have equal alternate angles.
How do i prove if the base angles of a triangle are congruent then the triangle is isosceles?
Suppose you have triangle ABC with base BC, and angle B = angle C. Draw the altitude AD.Considers triangles ABD and ACDangle ABD = angle ACD (given)angle ADB = 90 deg = angle ACDtherefore angle BAD = angle CADAlso the side AD is common to the two triangles.Therefore triangle ABD is congruent to triangle ACD (ASA) and so AB = AC.That is, triangle ABC is isosceles.
Prove diagonals are equal in a rectangle?
Suppose ABCD is a rectangle.Consider the two triangles ABC and ABDAB = DC (opposite sides of a rectangle)BC is common to both trianglesand angle ABC = 90 deg = angle DCBTherefore, by SAS, the two triangles are congruent and so AC = BD.
Write a two column proof for each of these problems given line ab is congruent to line ad and line ca is congruent to line ea prove angle abc is congruent to angle ade?
There cannot be a proof since the statement need not be true.
How do you prove that the diagonals of an isosceles trapezoid are equal?
Let's draw the isosceles trapezoid ABCD, where AD ≅ BC, and mADC ≅ mBCD. If we draw the diagonals AC and BD of the trapezoid two congruent triangles are formed, ∆ ADC ≅ ∆ BDC (SAS Postulate: If two sides and the angle between them in one triangle are congruent to the corresponding parts in another triangle, then the triangles are congruent). Since these triangles are congruent, AC ≅ BD.
How do you prove the diagonals of an isosceles triangle congruent?
You can't because triangles do not have diagonals but an isosceles triangle has 2 equal sides
How do you prove a trapezoid is isoceles?
To prove a trapezoid is isosceles, you need to show that the legs (the non-parallel sides) are congruent. This can be done by demonstrating that the base angles opposite these sides are congruent. You can use the triangle congruence postulates or the properties of parallel lines and transversals to establish the equality of these angles.
Prove that the diagonals of rectangle are equal?
prove any two adjacent triangles as congruent
How do you prove that a trapezoid is isosceles?
You prove that the two sides (not the bases) are equal in length. Or that the base angles are equal measure.
How do you prove an isosceles triangle?
an isisceles triangle is a triangle with atleast two sides congruent.
Is an equilateral triangle always or sometimes called an isosceles?
If you can only prove two sides of an apparently equilateral triangle to be congruent then you have to use isosceles.
What are necessary when proving that the diagonals of a rectangle are congruent?
A ruler or a compass would help or aternatively use Pythagoras' theorem to prove that the diagonals are of equal lengths
What are the proofs that a quadrilateral ia s parallelogram?
There are 5 ways to prove a Quadrilateral is a Parallelogram. -Prove both pairs of opposite sides congruent -Prove both pairs of opposite sides parallel -Prove one pair of opposite sides both congruent and parallel -Prove both pairs of opposite angles are congruent -Prove that the diagonals bisect each other
How can you prove a triangle ABC is isosceles if angle BAD is congruent to angle CAD and line AD is perpendicular to line Bc?
Given: AD perpendicular to BC; angle BAD congruent to CAD Prove: ABC is isosceles Plan: Principle a.s.a Proof: 1. angle BAD congruent to angle CAD (given) 2. Since AD is perpendicular to BC, then the angle BDA is congruent to the angle CDA (all right angles are congruent). 3. AD is congruent to AD (reflexive property) 4. triangle BAD congruent to triangle CAD (principle a.s.a) 5. AB is congruent to AC (corresponding parts of congruent triangles are congruent) 6. triangle ABC is isosceles (it has two congruent sides)
How do you prove In a circle or congruent circles congruent central angles have congruent arcs?
Chuck Norris can prove it
Prove that a rhombus has congruent diagonals?
Since the diagonals of a rhombus are perpendicular between them, then in one forth part of the rhombus they form a right triangle where hypotenuse is the side of the rhombus, the base and the height are one half part of its diagonals. Let's take a look at this right triangle.The base and the height lengths could be congruent if and only if the angles opposite to them have a measure of 45⁰, which is impossible to a rhombus because these angles have different measures as they are one half of the two adjacent angles of the rhombus (the diagonals of a rhombus bisect the vertex angles from where they are drawn), which also have different measures (their sum is 180⁰ ).Therefore, the diagonals of a rhombus are not congruent as their one half are not (the diagonals of a rhombus bisect each other).
