Opened 10 years ago

Last modified 6 years ago

#2697 new enhancement

Calculate should use an appropriate number of significant figures for trigonometric functions

Reported by: greenfeld Owned by: rwh
Priority: Unspecified by Maintainer Milestone: Unspecified
Component: Calculate Version: 0.92.x
Severity: Minor Keywords:
Cc: walter, lucyd Distribution/OS: OLPC
Bug Status: New


Calculate should use an appropriate number of significant figures for trigonometric functions. Right now it provides errors in the noise where it should provide a zero answer.

This potentially could confuse students if none of their other figures are that minuscule. Seen in Calculate-36 in OLPC 11.2.0 os13.

Examples seen on an XO-1.5 (using degrees; radians are similar):

  • sin(180) = 1.22460*10-16
  • cos(90) = 6.12303*10-17
  • tan(90) = 1.63317*1016 {technically I believe this is undefined, but Google's calculator makes the same mistake for this one entry}.

Change History (5)

comment:1 Changed 9 years ago by godiard

This ticket can be related to #2332

comment:2 Changed 7 years ago by lucyd

I propose the following idea for solving this issue.

  • Maintain a window of digits in the current computed value after decimal point
  • Check if any non-zero digit(significant figure) occurs in this window
  • If yes then go with the current format
  • If no then approximate the value to zero

This approach is for values between 0 and 1. Similarly we can check in a window of digits before the decimal point for approximating the value to infinity. All other cases follow the existing format.

comment:3 Changed 7 years ago by godiard

  • Cc walter added

comment:4 Changed 7 years ago by lucyd

  • Cc lucyd added

comment:5 Changed 6 years ago by vikramahuja1001

Will be automatically solved after solving #4814

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