atan not producing correct results.

Asked Sep 20 '16 at 15:06

Active Sep 20 '16 at 15:06

Viewed 35 times

So I try atan(4/3) and print it out and i get 0.78 radians but online atan(4/3) is ~0.927 radians. Why am i getting conflicting results?

std::cout << std::atan(4 / 3)<< std::endl;

that's literally all i did to check and its not giving me right answer unless google is lying to me as well. It should be giving me 0.927. even something like atan(7/3) is giving me an answer that is off by 0.06. What's going on here is this common problem?

asked Sep 20 '16 at 15:06

Giancarlo Gatti

5

4/3 == 1 (these are integers). Hence you have atan(1) – Sep 20 '16 at 15:07
1

Integer division truncates any decimals. – Some programmer dude Sep 20 '16 at 15:08
2

As a simple rule of thumb, **don't use `atan`**. If you'd used `atan2`, you wouldn't have encountered this problem (and it's other advantages are even more compelling). – Jerry Coffin Sep 20 '16 at 15:12
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Next time _divide and conquer_. You should have tested without the `atan`, and you'd have found that `4/3` is not what you thought it was. – Lightness Races in Orbit Sep 20 '16 at 15:42

atan not producing correct results.

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