NCERT Class 9 Solutions: Constructions (Chapter 11) Exercise 11.1 – Part 2 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Constructions of angle

Construction of Angle 45

Q-4 Construct the following angles and verify by measuring them by a protractor:

1.

2.

3.

Solution:

i) Step of Construction:

Ray of OA at Made ∠ AOC = 60°
  • Draw a OA ray
  • Construct
  • Construct
  • Bisect so that
  • So, that
  • Verification:
    • , with the protractor, we find

ii) Step of Construction:

Line Segment XA
  • Draw a line segment XA.
  • Construct and
    • ()
  • Bisect angle SAZ it bisector AR
  • So that,
  • Then in the angle of

iii) Step of Construction:

Two Bisector ∠ AOFand ∠ POE
  • Draw
    • Then
  • Draw the bisector of
  • Construct,
  • So that,
  • Then

Q-5 Construct an equilateral triangle, given its side and justify the construction.

Solution:

Equilateral Triangle
  • Take a ray CD with initial point C
  • C as centre and radius ()
  • Draw an arc of a circle, which intersects CD
  • Taking B as centre and with the same radius as before
  • Draw an arc intersecting the previously drawn arc, say at a point C
  • Join CA and BA

Then is the required triangle with side

Justification:

(Sum of the angles of a triangle)

(Sides opposite to equal angles are equal)

Developed by: