HP -15C Owner's Handbook Manual page 196

196 Section 14: Numerical Integration
Keystrokes
| ¥
0 v
| $
|R
Now you are ready to press ´f 0 to calculate the integral. When you
do so, you'll find that – just as with _ – the calculator will not display
the result right away, as it does with other operations. The HP-15C
calculates integrals using a sophisticated iterative algorithm. Briefly, this
algorithm evaluates f(x), the function to be integrated, at many values of x
between the limits of integration. At each of these values, the calculator
evaluates the function by executing the subroutine you write for that
purpose. When the calculator must execute the subroutine many times – as
it does when you press f – you can't expect any answer right away. Most
integrals will require on the order of 2 to 10 seconds; but some integrals
will require even more. Later on we'll discuss how you can decrease the
time somewhat; but for now press ´f 0 and take a break (or read
ahead) while the HP-15C takes care of the drudgery for you.
Keystrokes
´f 0
In general, don't forget to multiply the value of the integral by whatever
constants, if any, are outside the integral. In this particular problem, we
need to multiply the integral by 1/ π to get J
Keystrokes
|$
÷
Display
0.0000
3.1416
3.1416
Display
2.4040
Display
3.1416
0.7652
Run mode.
Key lower limit, 0, into Y-
register.
Key upper limit, π, into X-
register.
Specify Radians mode for
trigonometric functions.
π

θ)

cos (sin
0
(1):
0
J (1).
0
.
dθ