Area of a Deltoid (Kite)

🏆Practice area of a deltoid

How do we calculate the area of a kite?

The area of the kite can be calculated by multiplying the lengths of the diagonals and dividing this product by 2 2 .

Deltoid Area Formula

To facilitate the understanding of the concept of calculus, you can use the following drawing and the accompanying formula:

A=KM×NL2A=\frac{ KM\times NL}{2}

A8 - Area formula of the kite

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Test yourself on area of a deltoid!

Indicate the correct answer

The next quadrilateral is:

AAABBBCCCDDD

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There are many geometric shapes that can be found during the solving of engineering problems at all different stages of study, such as in high school, in matriculation exams, and even in psychometry. One of the less trivial shapes is the deltoid and, as part of the questions surrounding it, students are often asked to calculate the area of the deltoid.


What is the deltoid?

A deltoid is a polygon with four sides (that is, a quadrilateral) with two distinct sets of adjacent sides of equal length to each other.


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Types of Deltoids

There is a clear distinction between convex deltoid and concave deltoid.


Convex deltoid

Convex deltoid is a deltoid where the diagonals are inside and cross each other. The longer diagonal acts as a main diagonal, while the shorter diagonal acts as a secondary diagonal.

As you can observe in the following drawing, the main diagonal divides the deltoid into two overlapping triangles, that is, identical, and the secondary diagonal divides the deltoid into two isosceles triangles whose bases are adjacent and, indeed, identical. 

B2 - Convex deltoid


Do you know what the answer is?

Concave Kite

Concave kite is a kite where one of the diagonals (main diagonal) passes inside the kite and the other diagonal (secondary diagonal) passes outside the kite.

The concave deltoid can be described as a shape consisting of two isosceles triangles that share a common base, where one triangle contains the other triangle. The following drawing better describes the concave deltoid:

A3 - Concave Kite


  • When all sides of the kite have the same length, a rhombus is obtained, which is actually a special case of a kite.
  • Another special case of a kite is a square, when it is a case where all sides and all angles are of the same size. 

Properties of the Kite

  • The angles on the sides, or more precisely, the angles between the different adjacent sides of the kite, are of equal size.
  • The diagonals of the kite are perpendicular to each other 
  • The main diagonal in the convex kite (or its extension in the concave kite) crosses the secondary diagonal (in both cases), and therefore actually functions as a perpendicular bisector
  • The main diagonal equally divides (crosses) the main angles of the kite
  • Every convex kite has the possibility of enclosing a circle
  • In every kite, there are two sets of adjacent sides of equal size
  • As mentioned, a concave kite is characterized by a secondary diagonal located outside of it

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Practice on the Area of a Kite

Exercise 1

Given the kite KLMNKLMN whose area is 144144 cm², the meeting point of the diagonals LNLN and KMKM.

The area of the section KP must be calculated according to the attached drawing and the existing data:

  • LN=18LN=18 cm
  • A=144A=144 cm²
A5 - Given the kite KLMN

Solution:

This exercise is a reverse calculation, that is, we know the area and we are asked to calculate the length of the segment KPKP.

In the first step, we replace the data we know in the kite area formula.

We obtain:

A=(LN×KM) A=(LN\times KM)

144=(18×KM)2 144=\frac{(18\times KM)}{2}

We simplify the expression and obtain:

288=18×KM 288=18\times KM

KM=16 KM=16

In fact, we found the length of the second diagonal of the kite.

According to one of the properties of the kite, the diagonal LNLN divides the diagonal KPKP into two equal parts.

From here we obtain that KPKP is equal to 88 cm.

Answer:

KP=8 KP=8 cm


Examples and exercises with solutions for the Area of the Kite

Exercise #1

ABDC is a deltoid.

AB = BD

DC = CA

AD = 12 cm

CB = 16 cm

Calculate the area of the deltoid.

161616121212CCCAAABBBDDD

Video Solution

Step-by-Step Solution

First, let's recall the formula for the area of a rhombus:

(Diagonal 1 * Diagonal 2) divided by 2

Now we will substitute the known data into the formula, giving us the answer:

(12*16)/2
192/2=
96

Answer

96 cm²

Exercise #2

Shown below is the deltoid ABCD.

The diagonal AC is 8 cm long.

The area of the deltoid is 32 cm².

Calculate the diagonal DB.

S=32S=32S=32888AAABBBCCCDDD

Video Solution

Step-by-Step Solution

First, we recall the formula for the area of a kite: multiply the lengths of the diagonals by each other and divide the product by 2.

We substitute the known data into the formula:

8DB2=32 \frac{8\cdot DB}{2}=32

We reduce the 8 and the 2:

4DB=32 4DB=32

Divide by 4

DB=8 DB=8

Answer

8 cm

Exercise #3

Indicate the correct answer

The next quadrilateral is:

AAABBBCCCDDD

Video Solution

Step-by-Step Solution

Initially, let us examine the basic properties of a deltoid (or kite):

A quadrilateral is classified as a deltoid if:

  • It has two distinct pairs of adjacent sides that are equal in length.

In the question's image, we observe the following:

  • There are lines connecting A to B, B to C, C to D, and D to A, suggesting a typical quadrilateral.
  • The shape, given its central symmetry (as it is formed by joining these particular points which extend equal lines), is reminiscent of a symmetric or bilaterally mirrored formation.
  • Given the symmetry, it suggests all internal angles are less than 180 degrees, confirming the figure as a convex shape.

From this analysis, the quadrilateral satisfies the characteristic of having pairs of equal adjacent sides which confirms it as a deltoid. The symmetry suggests it is not concave (which occurs when at least one interior angle is greater than 180 degrees).

Therefore, the given quadrilateral, based on its properties and symmetry, is a convex deltoid.

Answer

Convex deltoid

Exercise #4

Look at the deltoid in the figure:

777444

What is its area?

Video Solution

Step-by-Step Solution

Let's begin by reminding ourselves of the formula for the area of a kite

Diagonal1×Diagonal22 \frac{Diagonal1\times Diagonal2}{2}

Both these values are given to us in the figure thus we can insert them directly into the formula:

(4*7)/2

28/2

14

Answer

14

Exercise #5

Indicate the correct answer

The next quadrilateral is:

AAABBBCCCDDD

Video Solution

Step-by-Step Solution

The problem requires determining if a given quadrilateral is a deltoid, and if so, whether it is convex, concave, or indeterminate based on the provided diagram. A deltoid, or kite, is generally defined as a quadrilateral with two pairs of adjacent sides being of equal length. Thus, a visual analysis is essential here as only diagrammatic data is available.

To address this, one must closely analyze the properties of the given quadrilateral in terms of similarity and its symmetry relative to a conventional deltoid structure:

  • Typically, you'd look for simultaneous symmetry or patterns indicating two equal-length adjacent pairs of sides.
  • After examining the diagram and the naming convention (vertices labelled A, B, C, D), see if it implies any such congruency visually or through label symmetry.
  • Lack of distinct clues for equal side pairs or diagonals prevents concluding its specific nature without additional information, especially since no specific length measures or angles are provided.

Given this and under diagram-only conditions, it's not possible to definitively prove that the shape is completely a deltoid (convex or concave). Therefore, without further data, identifying the indicated quadrilateral deltoid nature is beyond determining from the given data itself.

Consequently, the correct answer is: It is not possible to prove if it is a deltoid or not.

Answer

It is not possible to prove if it is a deltoid or not

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