Range of y: Solving Exercises with x=0

  • Context: High School 
  • Thread starter Thread starter SamitC
  • Start date Start date
  • Tags Tags
    Function Range
Click For Summary

Discussion Overview

The discussion revolves around determining the range of the variable y in the context of the equation y = √(1 - x²) when x is set to 0. Participants explore the implications of defining y as a function and the interpretation of square roots in this scenario.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the range of y when x equals 0, suggesting that y could be either 1 or -1.
  • Another participant asserts that y = √(1 - x²) indicates only the positive square root, thus defining y as a function with a single value for each input.
  • A different participant emphasizes that to consider both roots, one should write y = ±√(1 - x²), indicating that y can take on both positive and negative values.
  • There is a reiteration that the function y = √(1 - x²) is clear in its definition, leading to a range of 0 ≤ y ≤ 1.

Areas of Agreement / Disagreement

Participants express differing views on the interpretation of the square root function and the implications for the range of y. There is no consensus on whether y should include negative values or if it is restricted to non-negative values.

Contextual Notes

Some participants note the ambiguity in notation when discussing the square root and the need for clarity in defining the range of y based on the function's properties.

Who May Find This Useful

This discussion may be of interest to those studying functions, square roots, and their implications in mathematical exercises, particularly in the context of determining ranges and values of variables.

SamitC
Messages
36
Reaction score
0
Hello,
This is a very basic question but bothering me on some exercises.
upload_2016-7-19_0-14-33.png
,
upload_2016-7-19_0-14-33.png

Then how is the range of y is
upload_2016-7-19_0-15-49.png
? What if x is 0, then we can have y = 1 or y = -1.
While doing some exercises I encountered this issue and can't match the answers.
Thanks in advance
 
Physics news on Phys.org
For the most part, ##\sqrt{x}## indicates the positive square root value.

Since, in this case, y is a function, there is not the slightest ambiguity. Functions are only allowed to have one value for anyone input. So ##y=\sqrt{1-x^2}## refers only to the positive root.
 
  • Like
Likes   Reactions: SamitC
If you just write ##y = \sqrt{1-x^2}## then it is only the positive root. Otherwise you should write ##y = ± \sqrt{1-x^2}## to indicate that you consider both roots. And even this is a bit sloppy because it means ##y \in \{ ± \sqrt{1-x^2} \}##. I normally write ##y_{1,2} = ± \sqrt{1-x^2}##.
 
  • Like
Likes   Reactions: SamitC
.Scott said:
For the most part, ##\sqrt{x}## indicates the positive square root value.

Since, in this case, y is a function, there is not the slightest ambiguity. Functions are only allowed to have one value for anyone input. So ##y=\sqrt{1-x^2}## refers only to the positive root.
The function part made it clear. Thanks.
 
But the range isn't ##y\ge 0##. It's ##0\le y\le 1##.
 

Similar threads

  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 15 ·
Replies
15
Views
2K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 5 ·
Replies
5
Views
1K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 14 ·
Replies
14
Views
2K
Replies
8
Views
4K