takes
a number
and
returns the valuecorresponding
to that number. We can plot the point
as
ordinary points. In fact we can plot one pointfor
each allowed value ofand
hence obtain the graph of
The
graph of the function
is
shown below.
O Level Maths Notes: Functions – Domain, Range/Codomain
A functiontakes
a numberand
returns the valuecorresponding
to that number. We can plot the pointas
ordinary points. In fact we can plot one pointfor
each allowed value ofand
hence obtain the graph ofThe
graph of the function
is
shown below.
Some definitions are necessary:
Domain
The domain of a function is
the set of values thatcan
take. We can read the domain off the–
axis. For the functionthe
domain is the set of all real numbers but for
we
may not have
because
that would result in the division
which
is not defined. If for any reason the possible set of values ofis
restricted to certain values, for example
then
that is the domain.
Range or Codomain
The range or codomain of a
function is the set of values the functionmay
take. We read the codomain off the
–
axis. For the functionthe
codomain is the set of all real numbers becausemay
take any value, or alternatively, the equation
has
a solution
for allvalues.
Forwe
may not have
because
has
no solutions for
If
for any reason the possible set of values ofis
restricted to certain values, for example
then
that may restrict the codomain: for
ifthen
With
to
evaluatewhen
we
find