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F.  CALCULUS METHOD

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1. 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? 


Continue Lesson - Section G
 



Main Lesson | Sect A | Sect B | Sect C | Sect D | Sect E | Sect G | Sect H