Section 14

Numerical Integration

Many problems in mathematics, science, and engineering require calculating the definite integral of a function. If the function is denoted by f(x) and the interval of integration is a to b, the integral can be expressed mathematically as

I = ∫ba f (x)dx.

The quantity I can be interpreted

geometrically as the area of a region bounded by the graph of f(x), the x-axis, and the limits x = a and x = b.*

When an integral is difficult or impossible to evaluate by analytical methods, it can be calculated using numerical techniques. Usually, this can be done only with a fairly complicated computer program. With your HP-15C, however, you can easily do numerical integration using the f (integrate) key.

Using f

The basic rules for using fare:

1.In Program mode, key in a subroutine that evaluates the function f(x) that you want to integrate. This subroutine must begin with a label instruction (´b label) and end up with a value for f(x) in the X- register.

*Provided that f(x) is nonnegative throughout the interval of integration.

The f function does not use the imaginary stack. Refer to the HP-15C Advanced Functions Handbook for information about using fin Complex mode.

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