The sum of the angles in the deltoid is360° degrees.
The area of the deltoid contains the number of quadrilaterals that cover the selected parts of the plane.
The perimeter of the deltoid is the length of the thread with which we border the outline of the deltoid and is measured in units of length in meters or cm.
Concave Kite: A kite with one of its diagonals outside (like a kind of bowl).
On many occasions, when we sit on the beach facing the sea, we observe a good number of kites. Have you looked at their shape? This is a deltoid shape. The deltoid has a somewhat complicated form. It's a quadrilateral but not a square, and it has a shape similar to a rhombus and a parallelogram, but their definitions are different. In this article, we will learn what a deltoid is and how to identify it.
Who Else Belongs to the Kite Family?
Diamond Shape
Rhombus: All sides are equal vertical diagonals, diagonals that cross each other and bisect the angles, from each side we look at the quadrilateral of the kite. The rhombus is actually an equilateral kite.
Square: The most elaborate of the group: its diagonals are perpendicular and intersect; they cross the angles as in a rhombus, but in a square, the lengths of the diagonals are equal as in a rectangle. Also, from every side we look, we'll notice 2 isosceles triangles with a common base, so the characteristics of the kite will also be present in it. The square is a kite with equal sides and angles (all angles are right angles).
And, of course, the deltoid itself:
2 pairs of equal adjacent sides.
Deltoid Test
Why are the base angles equal in a kite?
We will use the definition of a Kite: 2 equilateral triangles with a common base
Therefore:AD=AB, and also CD=CB.
According to this:∢ABD=∢ADB Because the base angles in an equilateral triangle are equal
Also:∢BDC=∢DBC Base angles in an isosceles triangle are equal
Therefore:∢ABC=∢ADC We combine equal angles with equal angles so that the sum of the angles is equal (the total amount)
Even if we overlaid the triangles: △ABC with △ADC
We would obtain:
AB=AD (given)
BC=DC (given)
AC=AC (common side)
Therefore, we can conclude:
△ABC≅△ADC (according to the superposition theorem: side, side, side)
∢ABC=∢ADC (Corresponding angles in equal overlaid triangles)
As a result of the overlay, the kite principle can be deduced:
The main diagonal in the kite intersects the angles, crosses a secondary diagonal, and is perpendicular to it.
△ABC≅△ADC (according to the superposition theorem: side, side, side) Proven
Therefore:∢DAC=∢BAC
Also:∢BCA=∢DCA, Corresponding angles in equal overlaid triangles
The main diagonal in the kite intersects a secondary diagonal and is perpendicular to it.
According to the data:AD=AB After all, triangle ADB is an isosceles triangle.
In an isosceles triangle the vertex angle is perpendicular to the base and bisects it.
Therefore:AC⊥DB and also: DM=BM
From this, we can calculate the missing sides and the missing angles in the given kite:
ABCD is a kite,
FindX,Y,α,β in the given kite
X=AB=AD
X=5cm
According to the definition of a kite.
∢BAC=α=40° The main diagonal of the kite intersects the angles.
∢ACD=β=50° The main diagonal of the kite intersects the angles.
Y=3cm, the main diagonal in the kite intersects the secondary diagonal.
Calculating the perimeter of a kite is done by adding up all its sides:
5+5+4+4=18cm
And the calculation of the area of the deltoid is done using the product of the diagonals divided by two:
Calculation of the secondary diagonal:6cm=3+3=BD
And to calculate the length of the main diagonal ACwe use the Pythagorean theorem in right-angled triangles formed by the diagonals (as it has been proven to us that they are perpendicular to each other)
And therefore, in the triangle△ABO we obtain:
AO2+32=52
AO2+9=25
AO2=16 and we apply the
AO=4cm
And in the triangle△CBO we obtain:
CO2+32=42
9+CO2=16
CO2=7
2.645cm=CO
Therefore, the length of the main diagonal is equal to:
4+2.645=6.645cm
We can calculate the area of the deltoid:
26.645×6=19.935cm2
Deltoid Test: What is the necessary condition to get a deltoid?
Does every quadrilateral whose diagonals are perpendicular form a kite?