Kite and its Theorems

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In this section, we will discuss kite and its theorems.
In kite, adjacent sides are equal and long diagonal bisect the small diagonal at right angle.All interior angles are acute angles.
Theorem 1 : If a quadrilateral is a kite, then its diagonals are perpendicular.

GIVEN : AB ≅ CB and AD ≅ CD

PROVE THAT : AC ⊥ BD


Proof :

Statements	Reasons
1)AB ≅ AD	1) Given
2) BC ≅ CD	2) Given
3) AC ≅ AC	3) Reflexive (common side)
4) ΔABC ≅ ΔADC	4) SSS Postulates
5) ∠BAE ≅ ∠DAE	5) CPCTC
6) ΔABD is an Isosceles triangle.	6) By property of an isosceles triangle.
7) ∠ABE ≅ ∠ADE	7) Property of isosceles triangle.
8) ΔABE ≅ ΔADE	8) ASA postulate.
9) ∠AEB ≅ ∠AED	9) CPCTC
10)∠AEB +∠AED = 180	10) Linear pair angles are supplementary.
11) 2∠AEB = 180	11) Addition property
12) ∠AEB = 90	12) Division property
13) AC ⊥ BD and AE ⊥ BD	13) By property of perpendicular.

Theorem 2: If a quadrilateral is a kite, then exactly one pair of opposite angles are congruent.

Given : ABCD is a kite with AB ≅ AD and BC ≅ CD.

Prove that : ∠A ≅ ∠C.


Proof :

Statements	Reasons
1)AB ≅ AD	1) Given
2) BC ≅ CD	2) Given
3) AC ≅ AC	3) Reflexive (common side)
4) ΔABC ≅ ΔADC	4) SSS Postulates
5) ∠ABC ≅ ∠ADC	5) CPCTC

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Example based on kite and its theorems :
In a kite, ABCD,AB = x + 2 , BC = 2x + 1. The perimeter of kite is 48cm. Find x and also find the length of each side.

Solution :
As we know that, adjacent sides in a kite are equal.
∴ AB = AD and BC = CD.
Perimeter = sum of all the sides
P = AB + BC + CD + AD
48 = x + 2 + 2x + 1 + x + 2 + 2x + 1
48 = 6x + 6
⇒ 6x = 48 -6
∴ 6x = 42
x = 42/6
x = 7
∴ AB = AD = x + 2 = 7 + 2 = 9cm
and BC = CD = 2x + 1 = 2(7) + 1 = 14 + 1 = 15 cm

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Quadrilateral

• Introduction to Quadrilateral
• Types of Quadrilateral
• Properties of Quadrilateral
• Parallelogram and its Theorems
• Rectangle and its Theorems
• Square and its Theorems
• Rhombus and its Theorems
• Trapezoid (Trapezium)and its Theorems
• Kite and its Theorems
• Mid Point Theorem

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