Texas Instruments TI-92 Getting Started page 41

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Graphing Technology Guide: TI-92

Figure 5.102: Using nlnt(

5.12.2 Areas: You may approximate the area under the graph of a function y = f (x) between x = A and x = B with

your TI-92. To do this you use the F5[Math] menu when you have a graph displayed. For example, here are the

keystrokes for finding the area under the graph of the function y = cos x

between x = 0 and x = 1. The area is

∫

dx. First clear any existing graphs and then press COS X ∧ 2 )

represented by the definite integral

cos

ENTER followed by

GRAPH to draw the graph. The range in Figure 5.103 extends from –5 to 5 horizontally

and from –2 to 2 vertically. Now press F5[Math] 7[∫f(x)dx]. The TI-92 will prompt you for the lower and upper

limits which are entered by pressing 0 ENTER 1 ENTER. The region between the graph and the x-axis from the

lower limit to the upper limit is shaded and the approximate value of the integral is displayed (Figure 5.104).

Technology Tip: If the function takes on negative values between the lower and upper limits, the value that the

TI-92 displays it the value of the integral, not the area of the shaded region.

Figure 5.103: Graph of y = cos x

Figure 5.104: Graph and area

Technology Tip: Suppose that you want to find the area between two functions, y = f (x) and y = g(x) from x = A

and x = B. If f (x) ≥ g(x) for A ≤ x ≤ B, then enter the expression f (x) – g(x) and use the method above to find the

required area.