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### Minus sign

A minus sign (–) is always immediately associated with subtraction and negative numbers. That is logical, but there is more.

##### Subtraction

The calculation of

5 – 2 = 3

is clear. It becomes more difficult with

2  – 7 = –3

as now a negative number is created. A bit more complicated is

5 – (–2) = 7

as we must apply the well known rule

### + + = +   + – = –  – + = –  – – = +

##### Fractions

What should we think of

0.5 = 2−1

Here we have no negative values, and yet we use a minus sign. Many people think this is confusing. You could have written a fraction in stead We see here that numbers with negative exponents are just fractions, for This is because we work with decimal numbers.

##### Imaginary numbers

For the reciprocal of the imaginary unit you get

i –1 = –i

That is only possible because i has no real value.

##### Inverse functions

The minus sign is also used for inverse functions. The notation is

f (x) with the inverse  f  − 1(x)

On calculators we use

sin-1     for the inverse sine
sinh-1   for the inverse hyperbolic sine

and that is very simple.