Algebra 80  Multiplication with Complex Numbers  Summary and Q&A
TL;DR
Complex numbers can be multiplied by using the distributive property and combining like terms.
Key Insights
 🍉 Complex numbers can be multiplied using the distributive property and combining like terms.
 #️⃣ Multiplying a complex number by a real number scales the length of the vector without changing its direction.
 🔄 Multiplying a complex number by the imaginary unit (i) rotates the vector counterclockwise by 90 degrees without changing its length.
 ✈️ The modulus of a complex number is its distance from the origin on the complex plane, and the argument is the angle of its vector from the positive real axis.
 ✖️ When two complex numbers are multiplied, their arguments are added, and their moduli are multiplied.
Transcript
Hello. I'm Professor Von Schmohawk and welcome to Why U. In the previous lecture, we saw how complex numbers can be added or subtracted. In this lecture, we will demonstrate how complex numbers can be multiplied. We will start with a simple example multiplying the complex number 3+2i times 2 . Since this complex number is a sum of two numbers, ... Read More
Questions & Answers
Q: How can complex numbers be multiplied using the distributive property?
Complex numbers can be multiplied by using the distributive property and combining like terms. Each term in the first complex number is multiplied by each term in the second complex number and then combined. The result is a new complex number.
Q: What happens when a complex number is multiplied by a real number?
When a complex number is multiplied by a real number, the length of the vector representing the complex number is scaled by the real number. The direction of the vector remains unchanged.
Q: What happens when a complex number is multiplied by the imaginary unit (i)?
When a complex number is multiplied by the imaginary unit (i), the vector representing the complex number is rotated counterclockwise by 90 degrees. The length of the vector remains the same.
Q: How can complex numbers be graphically visualized using vectors?
Complex numbers can be graphically visualized using vectors on the complex plane. Each complex number is represented as a point on the plane, with the real part determining the horizontal position and the imaginary part determining the vertical position. The length of the vector represents the modulus or absolute value of the complex number, and the angle of the vector from the positive real axis represents the argument of the complex number.
Summary & Key Takeaways

Complex numbers can be multiplied by using the distributive property and combining like terms.

When a complex number is multiplied by a real number, the length of the vector is scaled without changing its direction.

When a complex number is multiplied by the imaginary unit (i), the vector is rotated counterclockwise by 90 degrees, while the length remains the same.