Engineering Board Exam Reviewer · Complex Numbers: Polar and Exponential Form · medium

Find the product (2, cis,40°)(3, cis,80°).

1. 6, cis,120°
2. 5, cis,120°
3. 6, cis,40°
4. 6, cis,60°

Answer

A. 6, cis,120°

Solution

Multiply the moduli and add the angles: 2·3=6 and 40°+80°=120°. The product is 6, cis,120°.

More Complex Numbers: Polar and Exponential Form questions

1. Simplify ( 15°+i 15°)8.
2. Evaluate (1+i)10.
3. Evaluate eiπ.
4. Write -1+i in polar form.
5. Write 4+4i in polar form.
6. Convert 10 60° to rectangular form.
7. Find the polar form of -3+3i.
8. Multiply using polar form: (2, cis,30°)(3, cis,60°)
9. Divide using polar form: 12, cis,80°4, cis,20°
10. Use De Moivre's Theorem to find (2, cis,30°)3.

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