Re: std.math module

2017-08-07 Thread greatsam4sure via Digitalmars-d-learn 

On Monday, 7 August 2017 at 04:47:56 UTC, Nicholas Wilson wrote:

On Sunday, 6 August 2017 at 23:33:26 UTC, greatsam4sure wrote:

import std.math;
import std.stdio;

cos(90*PI/180) = -2.7e-20 instead of zero. I will appreciate 
any help. thanks in advance.


tan(90*PI/180) = -3.689e+19 instead of infinity. What is the 
best way to use this module


in addition to what sarn said, tan(3pi/4) is a pole, not 
infinity. the mean of the left and right hand limits is 0


Thanks for the help. I will appreciate any resources for further 
reading

Re: std.math module

2017-08-06 Thread Nicholas Wilson via Digitalmars-d-learn 

On Sunday, 6 August 2017 at 23:33:26 UTC, greatsam4sure wrote:

import std.math;
import std.stdio;

cos(90*PI/180) = -2.7e-20 instead of zero. I will appreciate 
any help. thanks in advance.


tan(90*PI/180) = -3.689e+19 instead of infinity. What is the 
best way to use this module


in addition to what sarn said, tan(3pi/4) is a pole, not 
infinity. the mean of the left and right hand limits is 0

Re: std.math module

2017-08-06 Thread sarn via Digitalmars-d-learn 

On Sunday, 6 August 2017 at 23:33:26 UTC, greatsam4sure wrote:

import std.math;
import std.stdio;

cos(90*PI/180) = -2.7e-20 instead of zero. I will appreciate 
any help. thanks in advance.


tan(90*PI/180) = -3.689e+19 instead of infinity. What is the 
best way to use this module


That's just floating point maths for you.  You're not putting 
exactly pi/2 into cos, just a good floating point approximation.  
What you're getting out isn't exactly 0, either, just a good 
floating point approximation.  (-2.7e-20 is really, really small.)


Here's a good talk from DConf 2016: 
https://www.youtube.com/watch?v=97bxjeP3LzY


If you need exact maths, you'll need a symbolic manipulation 
library (never used one in D, but there was a discussion recently 
https://forum.dlang.org/thread/ghihookwgzxculshi...@forum.dlang.org).  You don't need this for most practical applications, though.

std.math module

2017-08-06 Thread greatsam4sure via Digitalmars-d-learn 

import std.math;
import std.stdio;

cos(90*PI/180) = -2.7e-20 instead of zero. I will appreciate any 
help. thanks in advance.


tan(90*PI/180) = -3.689e+19 instead of infinity. What is the best 
way to use this module