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digitalmars.D.learn - std.math module

reply greatsam4sure <greatsam4sure gmail.com> writes:
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
Aug 06
next sibling parent sarn <sarn theartofmachinery.com> writes:
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/ghihookwgzxculshibyc forum.dlang.org). You don't need this for most practical applications, though.
Aug 06
prev sibling parent reply Nicholas Wilson <iamthewilsonator hotmail.com> writes:
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
Aug 06
parent greatsam4sure <greatsam4sure gmail.com> writes:
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
Aug 07