Plot module: example sine integral
The example below shows the application of factorials, constants and subequations:
The definite integral
is the socalled sine integral with
Our task is to plot
As the equation Si(x) is quite long, we use subequations:
 t1= x  x^3/( 3*3! ) + x^5/( 5*5! )  x^7/( 7*7!) + x^9/( 9*9! )
 t2=  x^11/( 11*11! ) + x^13/( 13*13! )  x^15/( 15*15!) + x^17/( 17*17! )
 t3=  x^19/( 19*19! ) + x^21/( 21*21! )  x^23/( 23*23!) + x^25/( 25*25! )  x^27/( 27*27! )
The next steps are:

We declare the variable and enter start value, end value and step width. We intend to plot the graph
from 15 ≤ x ≤ +15. Note that the range of validity is dependent on the chosen
number of terms. You will see that, in this case, the validity range is samller
than the graph interval.
 Variable: x
 Start value: 15
 End value: 15
 Step width: 0.01
 We scale manually as below:
 Xaxis, left: 17
 Xaxis, right: 17
 Yaxis, top: 3
 Yaxis, bottom: 3
 And enter the function for Si(x):
 Sineintegral = t1 + t2 + t3 '@
We finalize the input with the return key and the graph of the function is then plotted:
(To plot module)
(To MAR Plus)
