Click here to purchase the entire book in PDF format. Complex Math Part 2 - Multiplication The multiplication of two complex numbers is similar to multiplying regular old real numbers. For example: $$(5 + j3) * (2 + j4) = (5 * 2) + (j3 * j4) + (5 * j4) + (j3 * 2)$$ (2.28) $$= (5 * 2) + (j * j * 3 * 4) + j(5 * 4) + j(3 * 2)$$ (2.29) $$= 10 + (12 * -1) + (j20 + j6)$$ (2.30) $$= 10 - 12 + j26$$ (2.31) $$= -2 + j26$$ (2.32) The shortened rule is: $$(a + jb)(c + jd) = (ac - bd) + j(ad + bc)$$ (2.33)