Wrong solution of a tangent using a matrix.

Hello!

For my studies I have to calculate the tangent of a full matrix (512x512) where the values are angles in radians,(getted by the function atan2).

The results are so high and that made me think there was sth wrong. So I did a test.

In the Command window I wrote l=atan2(0.3,0) which value is 1.5708. Then I calculated the tan(l) getting 1.6331 e+16.

That was obviously wrong because the real value is -272241.8.

After that, in the same Comand Window I wrote tan(1.5807) getting in this case the correct solution.

Why is this wrong? There is sth wrong using matrix or arrays?? Or is sth with atan2 and tan?

Thanks a lot in advance,

Celia

Answer 1

[Azzi Abdelmalek]

tan(1.5807)=-100.9693

How did you get -272241.8 ?

[Azzi Abdelmalek]

Celia commented

I wanted to say tan(1.5708), sorry!

[Azzi Abdelmalek]

I=atan2(0.3,0) % correspond to the angle of 0+0.3*j which is pi/2. It obvious that tan(pi/2)=inf. I do not understand why are you expecting another result

[Azzi Abdelmalek]

I=atan2(0.3,0)  %the result displayed is 1.5708, this is not the complete result

To understand type

format long
I=atan2(0.3,0)  % The more precise result

[Celia]

You are totally right. Thank you so much. Maybe I want to make everything complicated and I forget the simple things! Thaks again!