# Algebra 80 - Multiplication with Complex Numbers | Summary and Q&A

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August 9, 2019
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Algebra 80 - Multiplication with Complex Numbers

## TL;DR

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

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### 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.