Answer: Choice D
15(cos85° + i sin85°)
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Explanation:
Let's say we had these two general complex numbers, which are in polar form.
We can abbreviate them into the shorthand form
The notation "cis" stands for "cosine i sine".
Now that we have those complex numbers set up, multiplying them is as simple as saying this:
We do two basic things:
- Multiply the r values out front
- Add the theta values inside the the cis function
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With all that in mind, let's tackle the problem your teacher gave you.
The given complex numbers
abbreviate into
then those multiply to
which is why choice D is the final answer.
