Trig Equations: Solving for x in Given Ranges

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Homework Help Overview

The discussion revolves around solving trigonometric equations within the range of 0 to 360 degrees. The specific equations under consideration are 2sin x + sin x cos x = 0 and sin 2x = -1/sqrt(2).

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants explore the factorization of the first equation and the implications of the solutions for sin x. There is also discussion about the range of the cosine function and its relevance to the second equation. Questions arise regarding the possible values of 2x for the second equation and the interpretation of inverse functions.

Discussion Status

Participants are actively engaging with the problems, with some offering partial solutions and others questioning the validity of certain steps. There is an acknowledgment of the need for further exploration of the second equation, particularly regarding the values of 2x.

Contextual Notes

Some participants express uncertainty about their previous attempts and the correctness of their methods. There is a mention of a lack of familiarity with LaTeX, which may affect the clarity of future contributions.

xdeanna
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I had some questions on a test and i got these two wrong..

x is greater than or equal to 0 and x is less than or equal to 360

1) 2sin x + sin x cos x = 0
2) sin 2x = -1/sqrt(2)
 
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xdeanna said:
I had some questions on a test and i got these two wrong..

x is greater than or equal to 0 and x is less than or equal to 360

1) 2sin x + sin x cos x = 0
2) sin 2x = -1/sqrt(2)
Show us what you did and we'll go from there...
 
2Sin x + cos x sin x = 0
Sin x(2 + cos x) = 0
sin x = 0
x= sin^-1(0)
x=0degrees
or
2+ cos x= 0
cos x =-2
x= cos^-1(-2)
x=?

I did something different on the test but i think this is wrong too >.<

Don't make show what I did for #2 :(
 
Well, cos x = 2 does not have any solutions in x. This is because the range of cos x is [-1, 1]
 
xdeanna said:
2Sin x + cos x sin x = 0
Sin x(2 + cos x) = 0
sin x = 0
x= sin^-1(0)
x=0degrees
This is one solutions; there are two other numbers x in [0, 360] (deg.) for which sin(x) = 0. The inverse sine function will only produce numbers in the interval [-90, 90], in degrees. Think about where the graph of y = sin(x) crosses the x-axis.
xdeanna said:
or
2+ cos x= 0
cos x =-2
x= cos^-1(-2)
x=?

I did something different on the test but i think this is wrong too >.<

Don't make show what I did for #2 :(

OK, maybe I can help you get started in the right direction. If sin(2x) = -1/sqrt(2), then 2x = sin-1(-1/sqrt(2)). What are the possible values of 2x in [0, 720] (deg), so that sin(2x) = -1/sqrt(2)?
 
it's long time that I haven't posted anything here and so I forgot everything about latex. Will anybody here consider giving me link so that I can learn to type it.

then I'll post solution for this problem.
 

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