The 6th LiveMath document (IT4AMIntegArea6.thp) shows the
same speed-time graph of the car but it uses a calculus method, namely
integration, to find the area under the curve. "Integ" is the value of
the definite integral of y from x = a to x = b.
Question 17:
Compare the value of Integ with the limit in Q15 or the
value of TrapSum when n = 100. What do you observe?
Question 18:
Hence explain the significance of the definite
integral of y from x = a to x = b.
2.
The equation of the curve is given as a function f(x)
= x2 where x is called a wildcard variable in
LiveMath. To enter x, type ?x.
You can change the equation of the curve and the limits of integration,
a and b, to find the area under the curve from x = a to x = b. Try the
following and record your answers in the Worksheet.
(a) f(x) = x3 for x = 1
to 2,
[highlight RHS of f(x)
and type ?x^3 to get x3]
(b) f(x) = 5sin(x) for x = 0 to /2,
[use Ctrl Alt P to type;click
on graph to refresh]
(c) f(x) = x2 for x = –1
to 1,
(d) f(x) = x3 for x = –1
to 1,
(e) f(x) = x3 for x = –1
to 0.
Question 19:
When does the definite integral fail to give the area under
the curve?
Hint: Observe
the values of Integ for (d) and (e).
Question 20:
How do you modify it so that you can still calculate the area under
the curve?