Education Technology

# Knowledge Base

## Solution 11920: Calculating the Cumulative Sum of a Matrix on the TI-83 Family, TI-84 Plus Family, or TI-Nspire™ Handheld in TI-84 Plus Mode.

### How do I find the cumulative sum of a matrix on a TI-83 family, TI-84 Plus family, or TI-Nspire handheld in TI-84 Plus mode?

To find the cumulative sum of a matrix, input the matrix, exit the matrix editor, and then paste the cumsum() function on the home screen with the name of the matrix. The example below will demonstrate this procedure.

Note: To access the Matrix menu on the TI-83 press the [MATRX] key. On the TI-83 Family, TI-84 Plus Family, or TI-Nspire™ Handheld in TI-84 Plus Mode press [2nd][MATRIX].

Example: Find the cumsum() of matrix [3, -2, 6; 2, 2, 13]

Solution:

To enter the matrix:
• Press [2nd] [MATRIX] or [MATRX]
• Scroll to Edit
• Press [1] to access matrix A
• Input the dimensions [2] [ENTER] [3] [ENTER]
• Input the matrix entries, pressing enter after each entry as shown below
• Exit the matrix editor by selecting [2nd] [QUIT]

To find the cumulative sum using the cumsum( function:
• Press [2nd] [MATRIX]  or [MATRX]
• Scroll to MATH
• Press [0] [2nd] [MATRIX] [1] [)] [ENTER]

Please see the TI-83 family and TI-84 Plus family guidebooks for additional information.

NOTE: TI-Nspire users in TI-84 Plus mode may refer to the TI-84 Plus family guidebook.