Maths Practicals: Relations and Functions

Objective

To distinguish between a Relation and d function

Material required

Drawing board, coloured drawing sheets, scissors, adhesive, strings, nails etc.

1 st step

Take a drawing board/ a piece of plywood of convenient size and paste a coloured sheet on it

2nd step

Take a white drawing sheet and cut out a rectangular strip of 6 cm x 4cm and paste it on the left side of the drawing board (see fig. 6.1)

3 rd

Fix 3 nails on this strip and mark them as a,b,c (see Fig 6.1)

4 th step

Cut another white rectangular strip of 6 cm x 4cm and paste it on the right hand size of the drawing board

5th step

Fix 2 nails on the right side of this strip (see Fig 6.2) and mark them as and 2

Observation ( 1 st)

Join the nails of the left-hand strip to the nails of the right-hand strip by strings in different ways. Some of such ways are in Fig 6.3 - Fig 6.6.

Observation (2nd)

Joining nails in each figure constitute different ordered pairs representing elements of a relation

ordered pairs of fig 6.3

(a,1), (a,2), (b,1), (b,2) (c,2)

ordered pairs of Fig 6.4

(a,1), (b,1), (c,1)

ordered pairs in Fig 6.5

(a,2), (b,2), (c,2)

ordered pairs in Fig 6.6

(b,1), (c,2)

Application

Such activity can be used to identify different types of functions such as constant function, identity function, injective and surjective function