How do you use complex numbers?

Answer 1

Better get a textbook that explains this in more detail. You can also get a brief summary at Wikipedia, or other online sites.

In any case, here is a brief summary.

For addition and substraction, you add (or subtract) the real and imaginary parts separately. For example, (4 + 3i) + (7 - 2i) = 11 + 1.

For multiplication, multiply each part of one number with each part of the other number - and remember that i2 = -1. For example, (4 + 3i) x (7 - 2i) = 28 - 8i + 21i - 6i2 = 28 + 13i - 6(-1) = 34 + 13i.

Division is a bit more complicated. For example, to divide by (3 + 4i) you have to multiply numerator and denominator by the complex conjugate of this number, that is, change the sign of the imaginary part; in this case, (3 - 4i).

Multiplication and division are actually quite a lot easier if you convert the complex number to polar coordinates, that is, a distance and an angle. Here is a quick example: (4 angle 30 degrees) x (5 angle 20 degrees) = (4 x 5) angle (30 + 20 degrees) = 20 angle 50 degrees (a length of 20, at an angle of 50 degrees). Most scientific calculators have special functions to convert from rectangular to polar coordinates and back.