Construction Of Triangle

The Construction of Triangle is controlled by the congruential theorems. For Construction of Δs one needs to know three values (either sides S or angles A): SSS, SAS, ASA and right triangle ( HL or RHS ) .

Note that it is not sufficient to know only three angles.

In order to be able to construct a Δ from three segments, one of the segments must be shorter than the sum of the other two:
a < b+c, or b < a+c, or c < a+b

SSS Construction of Δ

Construct ΔXYZ in which XY = 4.5 cm, YZ = 5 cm and ZX = 6cm.

Step 1. Draw a line YZ of length 5 cm.

Step 2. From Y, point X is at a distance of 4.5 cm. So, with Y as center, draw an arc of radius 4.5 cm.

Step 3. From Z, point X is at a distance of 6 cm. So, with Z as center, draw an arc of radius 6 cm.

Step 4. X has to be on both the arcs drawn. So, it is the point of intersection of arcs. Mark the point of interaction of arcs as X. Join XY and XZ. ΔXYZ is the required triangle as shown in the figure.


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Practice Problems

1) We have PQ = 4 cm, PR= 3 cm and QR = 8 cm. Can a triangle with these measurements be possible ? Give reason also.

2) Draw a triangle with sides 2cm, 4cm and 6cm.

3) Draw a triangle of sides 6, 7 and 8cm

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Geometrical Constructions

• Basic Geometric Constructions
• Construction of Line Segment
• Bisecting a Line Segment
• Constructing Angles
• Bisecting Angles
• Constructing Parallel Lines
• Construction of Triangle (SSS)
• SAS Triangle Construction
• ASA Triangle Construction
• HL Triangle Construction (Rhs -construction)
• Constructing Quadrilaterals
• Constructing Triangles(when sum of sides or perimeter is given)

Geometry

7th grade math

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