Calculus is the mathematical analysis and description of things that are continuously changing.
It allows us to answer important questions such as
where is the change fastest, where are the highest and lowest points, how
is quantity accumulating etc. Such questions relate directly to the theoretical study
of curves and shapes, as well as real world problems involving
motion, growth, heat, populations, economics and many other things.
A particularly important aspect of this analysis is the ability to determine values and rates
precisely at an instant, without having to resort to approximations
A simple model of learning
As an example, think about learning something new—first you know nothing,
but then your knowledge gradually increases. As you become more comfortable and
familiar with the subject matter you probably learn
faster, until eventually you know most of what you need, and so your
rate of learning necessarily slows.
We can plot this process if we make the horizontal axis indicate the passage of time (T),
and the vertical axis indicate the knowledge acquired
(a value of 1 means learning complete). The
curve below is one possible representation of the process of smooth acquisition of
knowledge. This is called a learning curve.
We can plot the slope (i.e. the learning rate) vs time as well. Click the
Toggle slope curve button to see this curve.
The tools of calculus enable us to calculate the slope
curve—describing the rate of change, from the function
curve—describing the value at each point in time.
Consider this curve, and think about the rate of learning it indicates:
When is it fastest?
When is it slowest?
Click the Toggle tangent button, and drag to see the tangent
at each point in time.
Can you see the relationship between the slope of the tangent
and the rate of learning?
A more complicated model of learning
Of course learning does not always proceed so uniformly. A more realistic model
might include effects such as an initial period of rapid learning and
naïve confidence, followed by a realisation
of impending difficulty
and some associated loss of confidence, before stabilisation
and recovery leading to slower but more certain progress
and eventual mastery.
This situation is shown in the following plot:
Consider this curve, and think about the rate of learning it indicates.
Display the tangent to help if necessary.
Drag the green estimate crosses to construct what you believe the
slope curve (describing the learning rate) might look like in this case.
When you are confident with your estimate, plot the slope curve and
see how close you were.
Consider the points where the learning rate is maximum, zero, and negative.
Do these points relate to particular features of the original function?
Practice constructing slope curves
The plot below will show various curves. Use the green estimate crosses to practice
estimating the shape of the corresponding slope curve in each case.
As before, you can display the tangent line to help, and check your answer
by displaying the actual slope curve.
Click Next to bring up a new curve, and if
Easier is selected, some of the harder examples
will be excluded.
About the activity
Calculus comes in two flavours, but both share the
fundamental component of dealing with
Differential Calculus is the calculation
of instantaneous rates of change by considering the change in a function
over an infinitely small region, and Integral Calculus
which allows us to calculate how much of something there is by accumulating
infinitely small pieces.
The study of continuous, smooth change has been part of mathematics all the way
from Zeno of Elea, Eudoxus of Cnidus, and Archimedes of Syracuse in Ancient Greece,
through Descartes (the inventor of co-ordinate geometry) and Fermat (famous
for his Last Theorem), to Newton and Leibniz who independently invented calculus
in the last third of the 17th century (and argued over priority). Yet more than 150 years
would pass before
calculus was made fully rigorous through the work on limits by Cauchy, Weierstrass and others
in the mid 1800s.