Question

Using Mathematica, how do you type #1 and #2 in mathematica.

exlist[ (2]1 exlist[(7]1 exlistit Length(exList] 1 Note that the last command gives us the last element of the list. We can also use extist[l-1]] for this. Negative numbers count backwards from the end of the list: exlist-1] exlisti-2]1 exListlI-3]1 1. Write a command accessing individual list elements to find the sum of the second and fifth element of our list exList. Summing Over a List Another important tool for working with lists is the Sum ] function. If you just want to add up all the elements of a list, you can use Totall ], but for anything more complicated (like Simpson's Rule) we'll need more sophistication. The basic syntax for a sum is Sum[ fUl, li, a, b)] which gives us ie a Thus to add all the elements of our list, we could use: SuntexList [[1]], {1, 1, Length [exlist])) Sum[] is very powerful, and has many more options for more complicated formulas. For example, you can increment i by more than just 1 each time like this: Sum[ fli] , (i,a,bAi] ], where Δί is how much you want to change i each time. So to add only the even-numbered elements in our list, we would use: Sum[exListt[i], (i, 2, Length [exList], 2) 2. Write a Sum[] command to add only the odd-numbered elements of our example list.

Answer 1

1. For summing second and fifth element

exList[[2]] + exList[[5]]

2. For adding only odd-numbered elements

Sum[exList[[i]], {i,1, Length[exList], 2}]