Multiplying and subtracting coordinates

[OnceMore]

Hello,

I am hoping someone can help me understand a problem in a textbook. It just assumes you know how to do a littel bit of maths, which I don't, and haven't been able to figure out.

S₁₁ = 0.894 $\angle$ -60.6
S₂₁ = 3.122 $\angle$ 123.6
S₁₂ = 0.020 $\angle$ 62.4
S₂₂ = 0.781 $\angle$ -27.6

Then, how does |Δ| = |S₁₁ S₂₂ - S₁₂ S₂₁| = |0.696 $\angle$ -83|

I have tried different things, for example, converting between cartesian and polar etc, but nothing seems to get me there.

Multiplying the respective r parts, and subtracting as needed seemed to get me close there, but doing the same with the angles didn't work out.

Thanks.

-S

 

[OnceMore]

Oh, sorry ...I just figured it out!

Taking a break and coming back to it does help.

...just a thought, should I explain how it is done in case anyone else is looking to know this sort of thing?

I don't know what the protocol would be on that.

Slán
-S