Wrong solution of a tangent using a matrix.

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Celia
Celia 2013-9-27
评论： Celia 2013-9-30
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

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回答（1 个）

Azzi Abdelmalek
Azzi Abdelmalek 2013-9-27
tan(1.5807)=-100.9693
How did you get -272241.8 ?
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Azzi Abdelmalek
Azzi Abdelmalek 2013-9-27
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
Celia 2013-9-30
You are totally right. Thank you so much. Maybe I want to make everything complicated and I forget the simple things! Thaks again!

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