Exercise 17.1-Class 9th (P. Board)-Ytb

This exercise deals with basic knowledge of construction of triangles, rectangles and squares etc. We use this knowledge in our everyday life, for example in woodworking, graphic art, pattern making and metal arts. Geometrical figures, when intermixed, give an artistic look. In order to construct these figures we need a pair of compasses, Set Squares, Dividers and a straight edge. If the objects, for which we want to draw a geometrical design, are large in size, we may choose some suitable scale of reference so that the object can be designed on the available piece of paper.

Construction of a Triangle:

  1. Construction of a Triangle when two sides and the angle in between are given:

Draw one side AB, equal to the size given

At point A on the line AB, make the given angle and draw a line.

Cut the line at C equal to the size of the second side.

Draw a line joining the points B and C.

The triangle ABC constructed is the required Triangle.


  1. Construction of a Triangle when one side and two angles are given:

Draw the line AB equal to the given size of one side of the Triangle.

At point A, draw one of the required angles.

At point B, draw the second required angle.

Lines making the angles at A and B will meet at C.

The Triangle ABC so formed is the require Triangle.

  1. Construction of a Triangle when two sides and an angle opposite to the sides is given:

Draw a line AD of any length.

At point A, on the line, make the required angle.

Cut off the line at C, equal to one side of the triangle, to make the line AC.

Adjust the pair of compasses equal to the given second side of the triangle.

Put the pointer of the pair of compasses at point C and draw an arc on line AD.

The point where the pair of compasses cut the line AD will be our point B.

Draw a line between B and C

The triangle ABC, so formed is our required triangle.

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