+0  
 
+5
354
10
avatar

Having troubles (0.72∠-5π/36)/(1.38∠-17π/90)

Guest Nov 2, 2015

Best Answer 

 #9
avatar+26328 
+5

Thanks for pointing out the mistake guys - I've now corrected it.

Alan  Nov 7, 2015
Sort: 

10+0 Answers

 #1
avatar+91024 
0

Deleted

Melody  Nov 2, 2015
edited by Melody  Nov 2, 2015
 #2
avatar
+5

(0.72×(-5)×pi/36)/(1.38×(-17)×pi/90)

 

=150/391

Guest Nov 2, 2015
 #3
avatar
+5

They are complex numbers, or rather standard abbreviations for complex numbers.

0.72\(\angle (-5\pi/36)\) is a complex number with modulus 0.72 and argument \(-5\pi/36\).

The rule for division, (deduce it by writing the numbers in their cos + i.sin form), is divide the moduli and subtract the arguments.

So, for example \(12\angle(\pi/4)/2\angle(\pi/6)=6\angle(\pi/12).\)

Guest Nov 2, 2015
 #4
avatar+91024 
0

Silly me,  thank you :))

 

I  would like more explanation of the division please :)

Melody  Nov 2, 2015
 #5
avatar
+5

Put the numbers in their polar forms, \(r(\cos\theta+\imath\sin\theta)\), multiply top and bottom by the conjugate of the denominator and then, having multiplied out the brackets,  use some standard trig identities to simplify.

I have to go out now, I'll get back to it later if it's still a problem.

Guest Nov 2, 2015
 #6
avatar+26328 
+5

Or write it in the form

 

 \(r_1e^{i\theta_1}/r_2e^{i\theta_2}\rightarrow r_1e^{i\theta_1}\times \frac{1}{r_2}e^{-i\theta_2}\rightarrow \frac{r_1}{r_2}e^{i(\theta_1-\theta_2)}\)

 

 

Edited to correct the magnitudes.

Alan  Nov 2, 2015
edited by Alan  Nov 7, 2015
 #7
avatar
+5

Shoudn't that be r1 divided by r2 ?

Guest Nov 2, 2015
 #8
avatar
+5

yeah he raised the e^i theta to the power of negative 1 to get it on the numerator but forgot to do the same to r2.

Guest Nov 7, 2015
edited by Guest  Nov 7, 2015
 #9
avatar+26328 
+5
Best Answer

Thanks for pointing out the mistake guys - I've now corrected it.

Alan  Nov 7, 2015
 #10
avatar+91024 
0

Thanks guys  :))

Melody  Nov 7, 2015

23 Online Users

avatar
avatar
avatar
avatar
avatar
We use cookies to personalise content and ads, to provide social media features and to analyse our traffic. We also share information about your use of our site with our social media, advertising and analytics partners.  See details