Constructing a Quadrilateral

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C

ONSTRUCTING

A

Q

UADRILATERAL

WE SHALL LEARN HOW TO

CONSTRUCT A UNIQUE

QUADRILATERAL BY FOLLOWING

METHODS :-

When four sides and one diagonal are given.

When two diagonals and three sides are given.

When two adjacent sides and three angles are given.

When three sides and two included angles are given.

When other special properties are known.

CONSTRUCTING A QUADRILATERAL

WHEN FOUR SIDES AND ONE

DIAGONAL ARE GIVEN

Example : Construct a quadrilateral PQRS where PQ = 4cm, QR =

6cm, RS= 5cm, PS =

5.5cm and PR = 7cm

7 cm

Step 1 :-

Construct a triangle PQR using

SSS criterion.

7 cm

STEP 2 :-

WITH P AS CENTRE DRAW AN

ARC OF RADIUS 5.5 CM .

7 cm

STEP 3 :-

NOW, WITH R AS CENTRE DRAW AN

ARC OF RADIUS 5 CM INTERSECTING

ANOTHER ARC AT POINT S

7 cm

STEP 4 :-

NOW JOIN PS AND RS.

7 cm

PQRS is the required quadrilateral.

CONSTRUCTING A

QUADRILATERAL WHEN TWO

DIAGONALS AND THREE SIDES

ARE GIVEN.

Example : Construct a quadrilateral ABCD, given that BC =4.5 cm, AD = 5.5 cm, CD = 5 cm, AC = 5.5 cm and diagonal BD = 7 cm.

D

7 cm

A

C

B

STEP 1 :-

DRAW TRIANGLE ACD USING SSS

CRITERION

D

A

5.5 cm

C

STEP 2 :-

WITH D AS CENTRE DRAW AN

ARC OF RADIUS 7 CM.

D

A

5.5 cm

C

STEP 3 :-

NOW, WITH C AS CENTRE DRAW AN ARC

OF RADIUS 4.5 CM INTERSECTING

ANOTHER ARC AT POINT B.

D

A

5.5 cm

B

C

STEP 4 :-

JOIN AB, DB AND CB

D

A

5.5 cm

B

C

ABCD is required triangle

CONSTRUCTING A

QUADRILATERAL WHEN TWO

ADJACENT SIDES AND THREE

ANGLES ARE KNOWN

Example : Construct a M

120

 quadrilate ral MIST where

MI

3.5

cm,

M

S

75

120

,

IS

6.5

cm,

I

105

 and

T

105

I

75

S

Step 1 : -

Draw a line MI

3.5

cm and make an

MIX

105

.

X

M 3.5 cm

105

I

Step 2 : -

Measure IX

6 .

5 and name that point S.

Now make

ISY

120

.

Y

120

S

X

M 3.5 cm

105

I

Step 3 : -

Now make

IMZ

Z

75

Y

120

 S

X

M

75

105

3.5 cm I

STEP 4 :-

MARK THAT POINT T WHERE SY AND MZ

MEET.

Y

T

Z

120

 S

X

M

75

3.5 cm

105

I

MIST is the required

Quadrilateral .

CONSTRUCTING A

QUADRILATERAL WHEN

THREE SIDES AND TWO

INCLUDED DIAGONALS ARE

GIVEN.

Example : Construct a

D

Quadrilate ral ABCD, where

AB

4 cm, Bc

5 cm,

CD

6.5

cm,

B

105

 and

C

80

.

A 4 cm

B

C

Step 1 : -

Draw a line BC

5 cm and Draw an

 of 105

 along BX.

X

B

105

5 cm C

Step 2 : -

Measure BX

4 cm and name that point A.

X

A

B

105

5 cm C

Step 3 : -

Now make

BCY

80

Y

X

B

105

5 cm

80

C

Step 4 : -

Now, with C as centre,

Draw an arc of length 6.5

cm that cuts CY at point D.

Y

D

X

B

105

5 cm

80

C

X

B

Step5 : -

Join AD

Y

105

5 cm

D

80

C

ABCD is the required

Quadrilateral

.

CONSTRUCTING A

QUADRILATERAL WHEN

OTHER SPECIAL PROPERTIES

ARE KNOWN.

Some examples are :-

1.

Draw a square of side 5 cm.

2.

Construct a rhombus ABCD where AC =

6 cm, and BD = 7 cm.

EXAMPLE 1 :-

DRAW AN SQUARE ABCD OF

SIDE 5 CM.

has been given. Actually we have many more details with us, because the figure is special quadrilateral namely a square. We know that each of its angles is a

Right angle.

D

90

90

4.5 cm

90

90

C

A 4.5 cm

B

EXAMPLE 2 :-

CONSTRUCT A RHOMBUS ABCD

WHERE AC = 6 CM, AND BD = 7 CM.

Rhombus are Perpendicular bisectors of one another.

D

So, first we draw AC = 7 cm and construct its perpendicular bisector. Let them meet at O. cut off

3 cm lengths on either side of the drawn bisector . You get now B and

D.

A O

7 cm

B

C

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