# Phasers of inductors question

#### mbferguson

Joined Apr 23, 2017
94
I'm wondering how he goes from 120+3jw on the denominator to 120+j86.71

I tried figuring out mathematically to get that number but couldn't get it... is it something to do with polar coordinates?

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#### MrChips

Joined Oct 2, 2009
21,635
It has nothing to do with polar coordinates.
What is ω?

#### mbferguson

Joined Apr 23, 2017
94
It has nothing to do with polar coordinates.
What is ω?
The equation for Vin = 8cos(2pi96t - 171deg) volts

#### mbferguson

Joined Apr 23, 2017
94
It has nothing to do with polar coordinates.
What is ω?
I'm sorry that last response was wrong.
The equation is Vin = 7cos(2pi46t - 13deg)

#### MrChips

Joined Oct 2, 2009
21,635
The equation for Vin = 8cos(2pi96t - 171deg) volts
We must be looking at different jpg files.
I see vin = 7cos(2π46t - 13°)

#### MrChips

Joined Oct 2, 2009
21,635
I'm sorry that last response was wrong.
The equation is Vin = 7cos(2pi46t - 13deg)
So what is the value of ω?

#### mbferguson

Joined Apr 23, 2017
94

#### mbferguson

Joined Apr 23, 2017
94

#### MrChips

Joined Oct 2, 2009
21,635
OH MY GAWD that's a .3 not a times 3
Yep. Chalk that up to sloppy notation.

#### MrChips

Joined Oct 2, 2009
21,635
The other thing is, don't mix degrees and radians. That is another source of errors. cos( ) and sin( ) is always in radians.

#### mbferguson

Joined Apr 23, 2017
94
Hello again, I have another question. In this problem towards the bottom right of the page, he goes from "j20.36 + 88.10<-84.95" to "0 + j20.36". I'm assuming that the 88.10 cancels out somehow since the degree is negative, but I'd like some clarification on why that is. Also, I have no idea how he goes to the next step from that, where he says "7.755 -j87.76 / 7.755 - j67.40"

Thanks

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#### Papabravo

Joined Feb 24, 2006
14,206
Hello again, I have another question. In this problem towards the bottom right of the page, he goes from "j20.36 + 88.10<-84.95" to "0 + j20.36". I'm assuming that the 88.10 cancels out somehow since the degree is negative, but I'd like some clarification on why that is. Also, I have no idea how he goes to the next step from that, where he says "7.755 -j87.76 / 7.755 - j67.40"

Thanks
The horizontal line indicates that he is adding two complex quantities together. Since they are in different notations, he has to convert the polar representation of to a rectangular one. Then he can add two rectangular quantities together, and then convert back to polar. I disagree on this digits, but the method is sound.

I get 7.757 - j67.371 =67.817 ∠ -83.432°