Imaginary Definition and 362 Threads

An imaginary number is a complex number that can be written as a real number multiplied by the imaginary unit i, which is defined by its property i2 = −1. The square of an imaginary number bi is −b2. For example, 5i is an imaginary number, and its square is −25. By definition, zero is considered to be both real and imaginary.Originally coined in the 17th century by René Descartes as a derogatory term and regarded as fictitious or useless, the concept gained wide acceptance following the work of Leonhard Euler (in the 18th century) and Augustin-Louis Cauchy and Carl Friedrich Gauss (in the early 19th century).
An imaginary number bi can be added to a real number a to form a complex number of the form a + bi, where the real numbers a and b are called, respectively, the real part and the imaginary part of the complex number.

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  1. holly

    Unanswered Questions about Imaginary Tides: Help Needed!

    No one answered my burning questions about imaginary tides...these tides that have me in a bind, so to speak. So, *sniff, sniff* I will just blunder through the essay questions as best I can. Thanking everyone who has helped me all these weeks...I have a test Monday and feel confident...
  2. Z

    Finding Imaginary Numbers with Cosine of 3

    Question: Use the formula cos(x + iy) = cos(x)cos(iy) - sin(x)sin(iy) to find two imaginary numbers whose cosine is 3 My workings so far: cos(x)cos(iy) - sin(x)sin(iy) = 3 Therefore: cos(x)cosh(y) - i(sin(x)sinh(y)) = 3 cos(x)cosh(y) = 3 sin(x)sinh(y) = 0 sin(x) = 0 x = 0...
  3. V

    Derivative of an imaginary number

    I was just wondering if anyone knows the rule when taking the derivative of an imaginary number(i). For example: d(ix)/dx=? Thanks:)
  4. F

    Complex numbers. Imaginary part

    z1 = x + iy z2 = x - iy (Complex conjugate) Find: Im (1/z1) This is what I have tried to do: (1) z1*z2 = x^2 + y^2 (2) z2 / (x^2 + y^2) = 1 / z1 The answer is: -y / (x^2 + y^2) = I am (1 / z1) So my question is: Can I change z2 to I am (z2) and z1 to I am (z1) in...
  5. dduardo

    Ebay: Imaginary Girlfriend Service

    Just found this link in another forum I participate in. Just hilarious what people are willing to do to make a few bucks. http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2964350069&category=45208 I pretty sure some lonely physics or chem guy in here can use the service. :wink:
  6. STAii

    Does the size of the shell in 2s change when it has 2 electrons?

    Greetings. I am having problems understanding some things about shells. Actually, i am not even sure of if i am talking about shells (i am not sure this is the term in English, but i think it is). I have been taught that a shell is a place of space round the nuclei with a highest probability...
  7. I

    What is the Significance of the Imaginary Part in Relativistic Distance?

    Bonjour, Je suis nouveau à ce forum. :-) I am a newbie in this forum.. My question concerns the imaginary part in the relativistic distance. Is someone has some physical interpretations? Why should this sqrt(-1) exist in this equation? Not the mathematical explanation :-( but the physical...
  8. M

    Understanding Imaginary Time: A Simplified Explanation

    this is a concept which i don't believe has been properly described to me and i really don't understand well enough. can someone discribe it to me in relitivly simple terms.
  9. N

    What are the Top 5 States Considered Dull in America?

    Via conversation, stereotype and simple-daydreaming I have found out that there are States in America which I and others imagine to be dull, lifeless, the pits of the earth. Whether this is the real state of affairs in these states doesn't seem to matter. Some states like California and New York...
  10. E

    Solve 3-7i/2+3i: Imaginary Numbers

    Could someone PULEEZ explain how to work the following equation: 3-7i/2+3i For the life of me I cannot sqeeze this into my brain! Thank you in advance.
  11. A

    Solving an Algebra Problem: Imaginary Numbers

    I have an Algebra problem giving me trouble. I am supposed to determine without graphing, if the following equation is symetrical to the x or y-axis or to the origin. The equation is y^2 = -5/x^2. The problem is, I think that this is an imaginary number. Am I right about that?
  12. J

    What are imaginary numbers and how and why are they used in physics?

    What are imaginary numbers and how and why are they used in physics? Please could you try and make your answers as simple as possible and bear in mind that I have not even finished my GCSE course in maths yet.
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