# Trignometery - Imaginary Number

by Sara
(Brooklyn, NY)

simplify each number by using the imaginary number ? question is square root of -15

### Comments for Trignometery - Imaginary Number

 Oct 04, 2011 Square Root of a Negative Number by: Staff Question: by Sara (Brooklyn, NY) simplify each number by using the imaginary number ? question is square root of -15 Answer: √(-15) = √[(-1)*(15)] = √(-1)* √(15) = i * √(15) = i√(15) “i” is used to represent the square root of -1 because the Real Number System cannot represent the square root of -1. However, imaginary numbers are not imaginary in the sense that you can only imagine them. (Naming them “imaginary” was probably not the best choice of terminology.) Imaginary numbers are simply a special type of number. (Other special number types would include fractions or negative numbers.) Imaginary numbers were invented so equations such as x^2 + 4 = 0 can be solved. Imaginary numbers allow roots to be calculated for every polynomial. Solving many polynomials used in electrical engineering, mechanical engineering, and physics would be impossible without using imaginary numbers. In conclusion, let me illustrate how the invention of imaginary numbers compares with the invention of integers. Natural numbers (counting numbers) cannot be used solve the following type of problem: You have \$100, but spend \$150. What is your balance? Your balance is -\$50, but Natural numbers only include the positive numbers {1, 2, 3, 4, …}. You cannot use natural numbers to calculate a -\$50 value. The -\$50 is a value of \$50 less than nothing. How can you calculate less than nothing? To calculate a -\$50 value, you need a new type of number. That is why integers {…-4, -3, -2, -1, 0, -1, 2, 3, 4, …} were invented. Similarly, imaginary numbers were also invented to deal with a certain type of problem. Imaginary numbers were invented so equations such as x^2 + 4 = 0 can be solved. Thanks for writing. Staff www.solving-math-problems.com

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