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### Equals Sign with a Dot or a ~ Over It

```
Date: 01/25/2001 at 16:45:26
From: J. Leon Shohet
Subject: Meaning of a special equal sign

What does an equals sign with a dot (.) over it mean?
```

```
Date: 01/26/2001 at 16:39:35
From: Doctor Ian
Subject: Re: Meaning of a special equal sign

Hi,

That symbol means 'is nearly equal to'.

- Doctor Ian, The Math Forum
http://mathforum.org/dr.math/
```

```
Date: 12/04/2001 at 10:26:47
From: Kyle Lawrence
Subject: A symbol I don't know

What does an equals sign with a ~ over it mean?
```

```
Date: 12/04/2001 at 12:39:19
From: Doctor Ian
Subject: Re: A symbol I don't know

Hi Kyle,

It means 'approximately equals'.  For example, the value of pi is
approximately 3.14, so we might write

~
pi = 3.14

It's a subtle distinction, but an important one. Ignoring it can lead
you to results like this:

x^2 = 2

x = sqrt(2)

x = 1.41

x * x = 1.41 * 1.41

x^2 = 1.98

2 = 1.98

Note the difference:

x^2 = 2

x = sqrt(2)

~
x = 1.41

~
x * x = 1.41 * 1.41

~
x^2 = 1.98

~
2 = 1.98

Does this help?

- Doctor Ian, The Math Forum
http://mathforum.org/dr.math/
```
Associated Topics:
Elementary Definitions