Microsoft/calculator

Inaccurate results for trigonometric functions with exact results

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#309 opened on Mar 14, 2019

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Area: User ExperienceBugPri: 2help wantedtriage approved

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Description

Describe the bug The below examples of the trigonometric functions show a correct result at first. However, subtracting that result from itself results in a non-zero value, which shows that the results are represented as incorrect approximations internally, when it should be an exact result.

In DEG mode: arcsin(1) - 90 != 0 sin(30) - 0.5 != 0 In RAD mode: sin(π/2) - 1 != 0 but interestingly: cos(±π) + 1 == 0

This is a new issue spawned from the similar issue #222.

Steps To Reproduce

  1. Try the above calculations in scientific mode

Expected behavior Exact internal representation and result 0 for above calculations.

Device and Application Information (please complete the following information):

  • OS Build: 10 0 17763 0
  • Architecture: X64
  • Application Version: 10.1812.10048.0

Contributor guide

Research direction
Examine the implementation of arcsin, sin, and related functions in the calculator's math library. Look for cases where exact mathematical results (like 0, 0.5, 1) are being computed with floating point approximation and not stored as exact values. Consider using integer or rational representations for these common exact results.
Tech stack
cpp
Domain
backend
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C++floating point arithmetic
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65