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

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

Deleted

(0.72×(-5)×pi/36)/(1.38×(-17)×pi/90)

=150/391

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 \(12\angle(\pi/4)/2\angle(\pi/6)=6\angle(\pi/12).\)

Silly me,  thank you :))

I  would like more explanation of the division please :)

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.

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.

Shoudn't that be r1 divided by r2 ?

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.

Thanks guys  :))