How to Find the Symmetry of a Function – Easy Identification Tips

How to Find the Symmetry of a Function Easy Identification Tips

To find the symmetry of a function, I first consider the visual patterns displayed when the function’s graph is plotted.

Reflective symmetry in a graph occurs when two halves mirror each other across a line—either the y-axis for even functions or the origin for odd functions.

Identifying symmetry can simplify the graphing process and deepen understanding of the function’s properties.

For example, for a quadratic function given by $f(x) = ax^2 + bx + c$, the axis of symmetry is a vertical line that passes through the vertex of the parabola, which can be computed using the formula $x = -\frac{b}{2a}$.

A function graph reflected over the y-axis, with corresponding points equidistant from the axis

In practice, to determine if a function exhibits symmetry, I substitute $-x$ for $x$ and see what happens to the function.

If the replacement yields the original function, it demonstrates even symmetry; that is $f(x) = f(-x)$. If the function equals the negative of the original—$f(-x) = -f(x)$—this indicates odd symmetry.

However, if neither condition holds, then the function possesses no symmetry. Remember, finding the symmetry of a function is a powerful tool that can provide insights into the behavior of the function and guide us in graphing and solving real-world problems.

If you are keen on exploring the fascinating world of function symmetry, let’s dive in with some examples and solidify our understanding.

Steps for Finding Symmetry of Functions

When I look for symmetry in functions, I follow a specific set of steps to determine if a function is even, odd, or neither. 

A graph of a function with its axis of symmetry marked and the function reflected across the axis to show symmetry

Symmetry can tell us a lot about how the function behaves and its graphical representation.

First, I check for even function symmetry—symmetry about the y-axis. For this, I verify if replacing x with -x in the function’s equation yields the original function. In mathematical terms, a function ( f(x) ) is even if the following condition holds:

$$ f(-x) = f(x) $$

Next, I test for odd function symmetry—the origin symmetry. An odd function shows symmetry about the origin. This means that the function’s output changes sign when I replace x with -x. The condition for a function ( f(x) ) to be odd is described by the equation:

$$ f(-x) = -f(x) $$

If the function doesn’t satisfy either of these conditions, then it does not have y-axis or origin symmetry. However, it might still have symmetry with respect to another axis or line.

For graphical analysis, I reflect the function across the relevant axis or point. If the reflected graph overlaps with the original, I can confirm the symmetry. Common symmetric graphs include the circle (origin symmetry) and the parabola (y-axis symmetry).

Here’s a handy table summarizing the steps:

1Replace ( x ) with ( -x )( f(-x) = f(x) )
2Check if the original and equivalent equations are the same for even symmetryEven symmetry
3Check if the function’s output changes sign( f(-x) = -f(x) )
4If neither, check for other symmetriesGraphical analysis

Lastly, it’s important to remember that a function could have no symmetry at all, which is perfectly normal and quite common in more complex functions.

Methods for Finding Symmetry

When I explore the symmetry of a function in mathematics, I look for balance and harmony in its graph. Identifying symmetry is not just a visual exercise—it’s a crucial analytical tool to simplify a problem or understand the function‘s behavior.

  • To detect even function symmetry, which is symmetry about the y-axis, I check if the condition ( f(x) = f(-x) ) holds. If a function satisfies this condition, then its graph can be reflected over the y-axis, and the graph will remain unchanged.

  • For odd functions, there’s what we call origin symmetry. It means that the function has 180-degree rotational symmetry around the origin (0,0). Mathematically, I verify this by ensuring the function satisfies ( f(x) = -f(-x) ). If this stands true, the graph of the function can be rotated 180 degrees about the origin, and it will look the same.

Here’s a small table I keep in mind when considering symmetries:

Type of FunctionCondition for SymmetryLine of Symmetry
Even( f(x) = f(-x) )y-axis
Odd( f(x) = -f(-x) )Origin

I remember that simply having an even or odd degree in a polynomial doesn’t guarantee even or odd function behavior—these are specific types of symmetries revealed through algebraic testing.

Furthermore, if a function doesn’t seem to have a y-axis or origin symmetry, I may observe its graph for any other symmetrical patterns, particularly with respect to any line x = a, which would indicate a vertical line of symmetry. This concept particularly applies when I’m looking at the graph of a parabola, where the line of symmetry is located at its vertex.

By understanding symmetry in functions, I can quickly identify the characteristics of the function, predict its graph’s behavior, and simplify the complexity of certain mathematical problems.

Examples and Exercises

In exploring the symmetry of a function, it’s helpful to begin with a couple of definitions. A function is even if it has symmetry about the y-axis; this means that its graph is unchanged when reflected across the y-axis.

Mathematically, a function ( f(x) ) is even if ( f(-x) = f(x) ). On the other hand, a function is odd if it has symmetry about the origin, which means it is invariant under a rotation of 180 degrees about the origin, leading to the condition ( f(-x) = -f(x) ).

Let’s work through some problems to apply these concepts:

  1. Determine the Symmetry: Consider the following function, $ f(x) = x^2 $. To test for even symmetry, calculate ( f(-x) ) and compare it to ( f(x) ): $ f(-x) = (-x)^2 = x^2 = f(x) $ Since ( f(-x) = f(x) ), our function is even and symmetric about the y-axis.

  2. Odd Function Example: Examine $f(x) = x^3$. To check for odd symmetry, compute $ f(-x) $: $ f(-x) = (-x)^3 = -x^3 = -f(x) $ Thus, ( f(x) ) is an odd function with symmetry about the origin.

  3. Neither Even nor Odd: If we take $f(x) = x^3 + x $, and find $f(-x) = -x^3 – x$, neither of the conditions for even or odd symmetry are satisfied. This function is neither even nor odd.

To better understand these concepts, here are some exercises you can try:

  • For the function $ f(x) = \cos(x) $, establish whether it is even, odd, or neither.
  • Establish the symmetry of $ g(x) = \ln(x) + \sqrt{x} $.
  • Determine if $h(x) = e^{x} + x $ exhibits any symmetries.

Remember, if a function does not meet the criteria for being even or odd, it does not necessarily mean that it lacks any symmetry; it simply may not have symmetry along the y-axis or origin. It may possess other symmetrical properties or vertex points that can be explored.


In exploring the symmetry of functions, I’ve uncovered how the presence of symmetry can offer insight into a function’s behavior and simplify its graphical interpretation.

When analyzing whether a function is even, odd, or neither, I remember the core algebraic tests: for a function to be even, it must satisfy the condition $f(x) = f(-x)$, which is visually apparent when its graph is mirrored along the y-axis.

Conversely, a function is odd if it meets the requirement $f(-x) = -f(x)$, revealing itself through origin symmetry.

Recognizing these properties is not simply an academic exercise; it’s a practical tool. For instance, knowing a function is even can save me time when plotting because I only need to calculate half of the points.

Similarly, an odd function assures me that plotting a point $(x, y)$ automatically gives me its reflected point $(-x, -y)$ for free.

I also consider symmetry when I’m looking for roots or integrating functions. An even function demonstrates that zero can only cross at symmetric intervals, while odd functions assure me the integrals over symmetric intervals cancel out, possibly simplifying my work to zero.

In conclusion, the elegant dance of mathematics often leads back to symmetry. By recognizing and applying these properties, I gain efficiencies and a deeper understanding of the functions I work with.

Applying these concepts allows me to view the landscape of mathematical functions through a lens of balance and predictable structure.