Matrices and vectors in Scientific calculator plus 991 for Android
There are two ways to do linear algebra on the calculator. MATRIX Mode and VECTOR Mode keep four matrices (up to 7 × 7) or four vectors (2- or 3-dimensional) under names, so you type each one once and then calculate with MatA or VctB. The 2nd keyboard types a matrix or a vector straight into an ordinary calculation, for an answer you need only once. Both give exact answers where they exist: 2/3 rather than 0.667, √14 rather than 3.742.
- Matrices
- MatA to MatD, from 1 × 1 up to 7 × 7
- Vectors
- VctA to VctD, 2- or 3-dimensional
- Last result
- kept in MatAns or VctAns
- Without storing
- the 2nd keyboard's templates, in any calculation
A matrix is a grid of numbers and a vector is a single row of them, and the calculator takes both in the same two ways: stored under a name in a mode of its own, or typed into the calculation on the spot. This page says which to use, what the two have in common, and where each kind of calculation is covered.
Which page for which job
| The job | The page |
|---|---|
| Enter a matrix; add, subtract, scale and multiply | Matrix arithmetic |
| The determinant, the inverse, the transpose | Determinant, inverse and transpose |
| Rank, row reduction, trace, eigenvalues and eigenvectors | Rank, row reduction and eigenvalues |
| Enter a vector; the dot product and the cross product | Dot and cross product |
| A vector's length, the angle between two, a unit vector, a projection, a distance | Length, angle and projection |
Two ways in
The modes store. Press MODE and choose MATRIX or VECTOR. Each mode has four variables, MatA to MatD or VctA to VctD. You fill one in its editor once, and from then on a calculation uses its name: MatA × MatD, or VctC × VctD. The matrices stay stored while you work, so a long exercise on the same few matrices never means typing them again.
The 2nd keyboard types. On the ordinary calculation screen, 2nd turns the keyboard to its second page, which has a matrix template key and a key for each common matrix function. A matrix typed there is part of that one calculation and is not kept anywhere afterwards.
The manual's advice is the one to follow: the 2nd keyboard for a quick one-off answer, MATRIX or VECTOR Mode when you want to store matrices and reuse them. The functions are the same either way, and so are the answers.
The mode's menu
In MATRIX Mode everything comes from one menu, SHIFT 4 MATRIX; in VECTOR Mode the same menu is on SHIFT 5 VECTOR. Each has three sections.
- NAMES inserts a variable into the calculation you are typing: MatA to MatD and MatAns, or VctA to VctD and VctAns. Beside each matrix it shows the current size, such as [2×2]. The ✎ icon at the end of a row opens that variable in the editor instead.
- EDIT opens one of the four variables in the editor, to enter or change it. The paste icon at the end of a row inserts the variable instead.
- MATH lists the functions: Det, Inverse, Transpose and the rest for matrices; Dot, Angle, Normalize, Cross and Projection for vectors.
In MATRIX Mode, ALPHA 4 inserts a matrix straight into the calculation without storing it, for a matrix you will not need again.
The 2nd keyboard's keys
The second page holds the templates and the functions; the digits, + - × ÷, AC and = stay on the first page. So a calculation usually means turning the page once or twice: insert the template or the function on the second page, press 1st to go back for the numbers, and press = there. The second page has its own SHIFT, ALPHA and left right keys, so you can move around a matrix without turning back.
| Key | On its own | With SHIFT |
|---|---|---|
| [::] | Asks for a size, then inserts an empty matrix; the dialog opens on 3 × 3 | v2, an empty 2-dimensional vector (ALPHA: v3, a 3-dimensional one) |
| • | The dot product; between two matrices, their product | Cross, the cross product |
| Det | Det(, the determinant | Transpose( |
| Rank | MatrixRank(, the rank | Tr(, the trace |
| [ ]⁻¹ | Inverse(, the inverse | RowReduce( |
| EiValues | Eigenvalues( | Eigenvectors( |
| linear algebra | A searchable list of about sixty linear-algebra functions | clustering: the distance functions |
CLR, beside the search bar, clears the whole calculation without leaving the second page.
How big, and what is kept
- A matrix in MATRIX Mode is anything from 1 × 1 to 7 × 7, square or not. Edit size in the editor sets it, and resizing later keeps the elements that still fit and fills any new cell with 0.
- A vector in VECTOR Mode has two or three components. The Vector dimension dialog offers 1 x 2 and 1 x 3.
- An element may be a whole expression, a fraction or √2 as readily as a whole number; = works it out as you enter it.
- MatAns holds the last matrix result and VctAns the last vector result. The calculator writes them, so they have no ✎ icon: you can use them but not edit them.
When the sizes do not match
Most operations need their sizes to agree, and the calculator is quiet when they do not. Where there is nothing to compute, it shows the expression back unchanged instead of an answer; only a case that cannot be done at all reports an error.
- Adding or subtracting needs two matrices, or two vectors, of exactly the same size. A 2 × 2 plus a 2 × 3 comes back as it was typed. A vector subtraction may come back as an addition of the negated vector, which is still the expression and not a result.
- Multiplying two matrices needs the columns of the first to match the rows of the second.
- The determinant, the inverse, powers, eigenvalues and eigenvectors need a square matrix. The determinant of a 2 × 3 matrix reports an error.
- A dot product between a 2-dimensional and a 3-dimensional vector is rejected with an error message.
When an answer is not the one you expected, count the rows and columns first. In MATRIX Mode the NAMES list shows every stored size.
At a glance
| Keys | What they do |
|---|---|
| MODE | Opens the mode dialog, where MATRIX and VECTOR are |
| SHIFT 4 MATRIX | The matrix menu in MATRIX Mode: NAMES, EDIT, MATH |
| SHIFT 5 VECTOR | The vector menu in VECTOR Mode |
| ALPHA 4 | Inserts a matrix without storing it |
| 2nd | The 2nd keyboard, with the matrix and vector keys; 1st turns back |
| = | Confirms a cell and moves on; runs the calculation |
| AC | Clears the calculation; in an editor, clears the cell, then leaves |
Questions
How large a matrix can the calculator handle?
MATRIX Mode takes matrices from 1 × 1 up to 7 rows by 7 columns, in four variables named MatA, MatB, MatC and MatD. A fifth, MatAns, holds the result of the last matrix calculation, so an answer can go into the next one without being typed again. The NAMES list shows each variable's current size, such as [2×2], beside its name.
Should I use MATRIX Mode or the 2nd keyboard?
Use MATRIX or VECTOR Mode when a matrix or vector has more than one job to do: you enter it once, then combine names. Use the 2nd keyboard for a quick one-off answer: there are no variables, and you type each matrix into the calculation itself with the template key.
Why did my matrix calculation come back unchanged?
Because the sizes do not agree. Adding or subtracting a 2 × 2 and a 2 × 3 leaves nothing to compute, so the calculator shows the expression back instead of an answer. Only the cases that are impossible report an error, such as the determinant of a 2 × 3 matrix, or a dot product between a 2-dimensional and a 3-dimensional vector.
Can it work with vectors in three dimensions?
Yes. VECTOR Mode stores vectors in two or three dimensions, and the 2nd keyboard has a template for each, v2 and v3. Two 3-dimensional vectors have a cross product that is a vector; two 2-dimensional ones give a single number instead.
Related pages
- Enter matrices, then add, subtract and multiply them store MatA to MatD, then + − ×, powers and MatAns
- Determinant, inverse and transpose of a matrix Det, the inverse in exact fractions, Transpose, the identity
- Rank, row reduction, trace and eigenvalues of a matrix MatrixRank, RowReduce, Tr, Eigenvalues and Eigenvectors
- Enter vectors, then take the dot and cross product store or type vectors; + −, the dot product, the cross product
- Vector length, angle between vectors, unit vector, projection and distance Norm, VectorAngle, Normalize, Projection, EuclideanDistance
Written from the calculator's own manual and from the app itself, version 7.6.0; every figure is one the manual shows or a capture of the app proves. Last revised on 27 September 2026.
Bug reports and feature requests go to kimcuc@samatica.com — a person reads it.