What is a rhombus?
A rhombus is a 2D shape with four straight, equal sides and parallel pairs of opposite sides. This shape resembles a diamond and is the shape you’d expect to see in playing cards to represent the suit of diamonds. Rhombuses can be seen in everyday life in various ways. Items such as playing cards, kites, jewelry, signs, and crystals are or feature a rhombus.
What are the properties of a rhombus?
Like any shape, various properties define what a rhombus is. These properties are:
- A rhombus has four straight, equal-length sides.
- A rhombus has four vertices.
- A rhombus has two lines of symmetry.
- A rhombus has four interior angles. These angles are two acute angles and two obtuse angles.
- A rhombus has two pairs of parallel lines.
Interestingly enough, the qualities that make a shape a rhombus mean that all squares are rhombuses. Weirdly enough, though, not all rhombuses are squares, which you’ll be able to tell by checking through the above properties. It’s also worth remembering the following:
- All the sides of a rhombus have to be an equal length. So, like a square, if one or more sides are a different length, it’s not a rhombus.
- Opposite sides need to be parallel, and opposite angles must be equal; a parallelogram is also a rhombus.
- If you draw an X inside a rhombus by drawing a line from corner to corner, the angles in the middle should be a right angle.
How many lines of symmetry does a rhombus have?
Before checking the lines of symmetry of a rhombus, let’s start with the basics!
A line of symmetry is a line that cuts a 2D shape or 3D object into half. Upon drawing this line, two equal parts of the given form should have to match. Because of this, a line of symmetry – not surprisingly – can only be applied to symmetrical shapes like a rhombus.
To find the exact middle of a shape, you must look for two identical parts that are the mirror image of each other precisely. To draw the line, use a ruler, and if you’re trying to determine the sequence of symmetry of a paper shape, you can fold it in the middle.
Depending on the original shape, multiple lines of symmetry could be spotted. So how many does a rhombus have, then? The answer is 2. While a rhombus does have four equal sides, the angles inside are not all the same. Therefore, there are two ways to halve the quadrilateral shape.
How can I measure the area of a rhombus?
There are two different ways to calculate and measure the area of a rhombus. The first is by multiplying the diagonals of a rhombus – these are the two interior intersecting lines that make a cross shape. So if the horizontal diagonal is 4 cm and the vertical diagonal is 5 cm, the rhombus in question would have an area of 20 cm.
The second way to calculate and measure the area of a rhombus is by using the base and height. Similarly to using the diagonals, you must multiply the base and size to get the area. So if a rhombus has a base of 6 cm and a height of 10 cm, it would have an area of 60 cm.
Is a rhombus the same as a diamond shape?
There is an entire discussion about this question, and there are different opinions, even among teachers. We have to come back to the definition of the rhombus, a parallelogram in which all the edges are of equal length. According to parallelogram properties, in a rhombus, the diagonals bisect the angles and are perpendicular to each other.
Now, looking at a rhombus’s definition and properties, we can decide whether a rhombus shape and a diamond shape are identical. You might think a rhombus is the same shape as a diamond, and you’re not wrong.
There are different diamond shapes, just like there are different rhombus shapes. Many shapes can be classed as multiple shapes by changing their orientation or looking at them differently. Similarly, a rhombus can be classed as a shape despite not looking like one.
The rhombus is often called a diamond in a lot of different contexts. For instance, the diamonds suit playing cards, resembling an octahedral diamond’s projection. But most of the time, it is used as a synonym for rhombus.
Is ‘diamond’ appropriate in geometry lessons?
The diamond shape is not usually a formal mathematical term teachers use in their geometry lessons. Not everyone agrees that diamond shapes and rhombi are the same.
Some people associate this shape with a kite and call it like this, while others call it a tilted square. However, many people use this term when discussing geometric shapes.
So, returning to our question, is it appropriate to use ‘diamond shape’ during geometry lessons when we want to teach children about rhombus? This name is not formally included in primary school lessons because it wasn’t adopted officially, but there is nothing wrong with using it, either.
The approach might vary depending on what and how you are trying to teach.
If you want to ensure that everyone in your classroom understands a concept in the same way and make the lesson as concrete as possible, sticking to the geometry vocabulary might be the best idea.
That would mean teaching children that the figure is called a ‘rhombus.’ This direction might fit you if you take into consideration that, just like the ‘oval,’ the diamond shape doesn’t have a precise definition, so you’re sticking to the term that has one.
However, if you want to help your children identify a diamond when they see one or what shape they should imagine when they hear this word, it’s nothing wrong with teaching them about it. Just keep in mind that diamond shape is an informal term that doesn’t have a geometrical definition in place.