Page 208 - Start Up Mathematics_7

Steps of Construction: X

1. Draw a line segment YZ measuring 5.5 cm.
2. Draw an arc of radius 5.5 cm taking Y as centre.
3. Draw another arc of radius 5.5 cm taking Z as 5.5 cm
centre cutting the previous arc at X. 5.5 cm
4. Join XY and XZ.
5. XYZ is the required triangle.

Y 5.5 cm Z
Example 4: Draw a ∆ PQR with PQ = 4 cm, QR = 3.6 cm and PR = 4 cm. P
What type of triangle is this? 4 cm
Solution: Construction: Draw a rough sketch of ∆ PQR and mark 4 cm
the given dimensions.
Steps of Construction: Q 3.6 cm R
1. Draw a line segment QR measuring 3.6 cm. P
2. Draw an arc of radius 4 cm taking Q as centre.
3. Draw another arc of radius 4 cm taking R as centre
cutting the previous arc at P. 4 cm 4 cm
4. Join PQ and PR.
5. PQR is the required triangle.

We observe that it is an isosceles triangle.
Q 3.6 cm R

Maths Lab Activity

Objective: Construction of an equilateral triangle by
paper folding

Step 1: Take a rectangular paper with base AB.

Step 2: Fold the paper vertically into 2 halves to A B
obtain the perpendicular bisector through the
midpoint D of the width AB. Press to form
the crease and then unfold it.

Step 3: Next, make a fold so that the corner point B
falls on the perpendicular bisector. Press it A D B
when the fold passes through A.

Step 4: Make another fold along AB (as shown) so B

that the vertical length along A coincides with E
AE. Press it to form a crease.

A A

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