- #1

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## Homework Statement

(2 CIS (pi/6))*(3 CIS (pi/12))

## Homework Equations

Also what is CIS? I believe it's Cos+i*sin but how do you use it?

## The Attempt at a Solution

i simplified it to

6 CIS (pi/12)

How do i turn it into cartesian?

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- Thread starter Stripe
- Start date

- #1

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(2 CIS (pi/6))*(3 CIS (pi/12))

Also what is CIS? I believe it's Cos+i*sin but how do you use it?

i simplified it to

6 CIS (pi/12)

How do i turn it into cartesian?

- #2

tiny-tim

Science Advisor

Homework Helper

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Hi Stripe!

(have a pi: π )

I've never seen "CIS" before, but I'll guess you're right, and that it's cos + i*sin.

Now use De Moivre's theorem … cosθ + isinθ = e^{iθ}

And Cartesian form simply means in the form x + iy (as opposed to polar form, which is in the form re^{iθ} )

(and no, it's not 6 CIS (π/12))

(have a pi: π )

I've never seen "CIS" before, but I'll guess you're right, and that it's cos + i*sin.

Now use De Moivre's theorem … cosθ + isinθ = e

And Cartesian form simply means in the form x + iy (as opposed to polar form, which is in the form re

(and no, it's not 6 CIS (π/12))

Last edited:

- #3

HallsofIvy

Science Advisor

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The important thing about that notation is that [itex](Cis(\theta)*Cis(\phi)= Cis(\theta+ \phi)[/itex].

So you have correctly deduced that [itex](2Cis(\pi/6))(3Cis(\pi/12)= 6 Cis(3\pi/12)= 6 Cis(\pi/4)[/itex]

Now, just use the definition: [itex]6 Cis(\pi/4)= 6 cos(\pi/4)+ 6i sin(\pi/4)[/itex].

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