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Is i any less real than -1?

Why do we call i an imaginary number, is it really more imaginary than a negative number? Can you have negative something? What makes a number "real" and what makes it "imaginary?"

Update:

A common opinion is that it is imaginary, because there is no root of -1 in the Reals. Commonly, mathematicians would pose this as: the function x^2+1 has no roots in the polynomial ring over the Reals. But consider 1/2: there is no solution to roots of the polynomial 2x-1 in the polynomial ring over the itegers, even though this polynomial is in that ring. So, you could just as easily say that 1/2 is not real because there is no 1/2 in the integers. What do you think about that?

10 Answers

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  • 2 decades ago
    Favorite Answer

    I don't think it is possible to actually comprehend i, since it is the square root of -1. We don't know of any numbers whose square equals a negative number, which is why i is imaginary. When you square a negative number, the negative signs cancel out, giving a positive value. In order to get a negative square, you would have to have some sort of crazy negative/positive amalgam or some type of half-positive-half-negative number.

    imaginary numbers are ones that aren't possible in our normal, continuous mathematics. They are virtually always represented with i, since i is the basis for imaginary numbers.

    I would say that yes, you can have negative somethings, even though you have to imagine them (which is why "imaginary numbers" might be a misnomer). For example, if you have six apples but you are hungry, you might think of your hunger as -2 apples.

  • 2 decades ago

    have u heard of the number line?

    well if u haven't then the number line is a 1 dimensional number system.

    basically it's a straight line (say X axis) that contains all possible real numbers from -infinity to +infinity. any number located on this line is what we call a real number (even 1/2 lies on this line, if u have used a graph, it will be more clear)

    the imaginary number 'i' = sqrt(-1) introduces another line (say Y axis) perpendicular to the first line we considered, which intersects the number line (X axis) at 0 (zero). the imaginary number thus introduces a 2 dimensional number system (a plane, say X-Y plane)

    the value i = sqrt(-1) was encountered in mathematics and electrical engineering but it could not be plotted on the 1 dimensional number line. so we went in for the 2nd dimension that includes all multiples of 'i' along a line. the result was a plane in which every number ever encountered in mathematics could be plotted on a graph sheet

    P.S.

    sqrt(-1) = square root of -1

  • albert
    Lv 5
    2 decades ago

    Your example of 1/2 indicates that you are missing the

    difference between whole numbers and rational numbers.

    Rational numbers can be expressed as the ratio of two

    whole numbers, such as 1/2, 2/3 etc. There is a hierarchy

    of numbers. The most restrictive are positive whole numbers.

    More inclusive are positive and negative whole numbers.

    More inclusive are rational numbers which include whole

    numbers. So whole numbers are rational, but rational

    numbers are not necessarily whole. On another separate

    branch of numbers are the irrationals such as pi and e.

    They cannot be expressed as a ratio of two whole numbers

    and as a decimal, and they do not repeat. But irrationals

    can still be compared to rationals(i.e., pi<4). The

    inclusive set of rationals and irrationals are called real

    numbers. The terms real and rational and irrational are

    not meant to be interpreted philosophically or with every

    day semantics, rather they're meant as a loose intuitive

    label. So when we come up with the imaginary numbers let's

    remember that imaginary is just a label. Now if we think

    of the reals in one dimension(left and right on the number

    line), then we can think of the imaginaries in another

    dimension(up and down). So you can't compare imaginaries

    to reals by the use of "greater than" or "less than". But

    you can compare their relative magnitudes. For example,

    2i has a magnitude of 2 and 3 has a magnitude of 3. So

    3 is greater in magnitude than 2i.

    The combined set of reals and imaginaries are called

    complex numbers,(i.e., 3+4i) which, by the way has a

    magnitude of 5. And instead of being on a number line,

    they lie in the complex plane. And they have a "real"

    purpose in math. For example, -1 has 3 cube roots as

    you would of course expect. They are -1, 1/2+i(sqrt(3))/2

    and 1/2-i(sqrt(3))/2 . Multiply them out, just for fun.

    Now, finally getting back to English semantics,

    negative numbers are not pessimistic, irrational numbers

    are no less sane than rationals and imaginary numbers

    do not dwell in the world of elves, fairies and unicorns.

  • 2 decades ago

    Negative Numbers cannot have square roots because anything squared is ALWAYS positive NEVER negative. So the Imaginary Number System deals with(-1)^0.5 or the square root of One. IT is non-existant and is only a concept to work with!

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  • 2 decades ago

    It is easier to explain it with a number line. In theory, you can find and spot any real number on a number line, for instance, Pi, e, 3, 2.3443, 1/2, 1/3, and sqr(2), sqr(5). However, can you identify sqr(-1)on the number line? is between which two numbers? we call i imaginary number, because we dont really see it on a number line, like an imaginary friend.

  • 2 decades ago

    Numbers are what they are they are, numbers. The "real" are very tangible in the sense they can represent money, speed, and weight just to name a few. Negative numbers are also used to represent things like debt. Just as the imaginary numbers are used to represent things in electrical circuits.

    But when it comes to what is real and what is imaginary, simply put have you ever tripped over the number "1" or "i".

  • 2 decades ago

    New types of numbers were needed over the history of mathematics for different situations. Originally there were the counting numbers and zero.

    Then we needed to be able to solve for x + 1 = 0. Thats when negative counting numbers came about.

    Then we needed to solve for 3x = 2. That is when the rationals arrived.

    Then we needed to solve for x^2 = 2. That is when the irrationals came.

    Then we needed to solve for x^2 = -2. Thus the complex numbers.

    So new numbers arose when they were needed. There was a time when irrationals were incomprehesible to people, just like maybe the complex numbers are today.

  • 2 decades ago

    These names are not intended to be a "definition" of real, negative, irrational, trascendent, imaginary... They are only "metaphoric". For example, "negative numbers" simulate a "negative income", i.e. a sum you are spending, when you are considering positives the sum you are receiving, and so on.

  • 2 decades ago

    There are both imaginary. Unless you're an electrical engineer. Then i is real and j is imaginary.

  • fred
    Lv 6
    2 decades ago

    they are very real in an electrical circuit containing inductnce/capacitance.

    the axis is labled j by electricians to avoid confusion with current which is normally denoted by i. it is still sq root -1 though

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