# lhs

Left side (LHS) of equation

## Syntax

``lhsEqn = lhs(eqn)``

## Description

example

````lhsEqn = lhs(eqn)` returns the left side of the symbolic equation `eqn`. The value of `eqn` also can be a symbolic condition, such as x > 0. If `eqn` is an array, then `lhs` returns an array of the left sides of the equations in `eqn`.Conditions that use the `>` or `>=` operator are internally rewritten using the `<` or `<=` operator. Therefore, `lhs` returns the original right side. For example, ```lhs(x > 0)``` returns `0`.```

## Examples

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Find the left side of the equation $2\mathit{y}={\mathit{x}}^{2}$ by using `lhs`.

First, declare the equation.

```syms x y eqn = 2*y == x^2```
`eqn = $2 y={x}^{2}$`

Find the left side of `eqn` by using `lhs`.

`lhsEqn = lhs(eqn)`
`lhsEqn = $2 y$`

Find the left side of the condition $\mathit{x}+\mathit{y}<1$ by using `lhs`.

First, declare the condition.

```syms x y cond = x + y < 1```
`cond = $x+y<1$`

Find the left side of `cond` by using `lhs`.

`lhsCond = lhs(cond)`
`lhsCond = $x+y$`

For an array that contains equations and conditions, `lhs` returns an array of the left sides of those equations or conditions. The output array is the same size as the input array.

Find the left side of the equations and conditions in the vector `V`.

```syms x y V = [y^2 == x^2, x ~= 0, x*y >= 1]```
`V = $\left(\begin{array}{ccc}{y}^{2}={x}^{2}& x\ne 0& 1\le x y\end{array}\right)$`
`lhsV = lhs(V)`
`lhsV = $\left(\begin{array}{ccc}{y}^{2}& x& 1\end{array}\right)$`

Because any condition using the `>=` operator is internally rewritten using the `<=` operator, the sides of the last condition in `V` are exchanged.

Find the left side of a symbolic equation that involves symbolic matrix variables.

Create the symbolic matrix variables and the symbolic equation.

```syms A [2 2] matrix syms B [2 1] matrix syms C [1 2] matrix eqn = B*C == A*A - 2*A + eye(2)```
`eqn = $B C={\mathrm{I}}_{2}-2 A+{A}^{2}$`

Find the left side of the equation by using `lhs`.

`lhsEqn = lhs(eqn)`
`lhsEqn = $B C$`

## Input Arguments

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Equation or condition, specified as a symbolic equation or condition, or a vector, matrix, or multidimensional array of symbolic equations or conditions.

Data Types: `sym` | `symfun` | `symmatrix` | `symfunmatrix`

## Version History

Introduced in R2017a

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