Trignometric inequality problem

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Another way to proceed would be to use the unit circle trigonometry to evaluate sin(x) for various values of x.
  • #1
needingtoknow
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Homework Statement



Given that -pi < x < pi, solve the following inequality in radians

root(2) - 2sin(x-(pi/3)) < 0


The Attempt at a Solution




root(2) - 2sin(x-(pi/3)) < 0
- 2sin(x-(pi/3)) < -root(2)
sin(x-(pi/3)) > (root(2))




-pi<x<-pi

-pi - (pi/3) < x - pi/3 < pi - (pi/3)

-4pi < x-(pi/3) < 2pi/3


and I know that -5pi/4 and pi/4 fit the new range as a result of the translation pi/3 I just don't know what to do with them. Can someone please help?


That is so far what I have got I do not know where to proceed from
 
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  • #2
needingtoknow said:

Homework Statement



Given that -pi < x < pi, solve the following inequality in radians

root(2) - 2sin(x-(pi/3)) < 0

The Attempt at a Solution

root(2) - 2sin(x-(pi/3)) < 0
- 2sin(x-(pi/3)) < -root(2)
sin(x-(pi/3)) > (root(2))
You have a mistake in the 3rd line. You can go from the first inequality directly to this inequality by adding 2sin(x - ##\pi/3##) to both sides.

##\sqrt{2} < 2sin(x - \pi/3)##
needingtoknow said:
-pi<x<-pi
? This is saying that ##-\pi## is less than itself, which is not true. How did you get this?
needingtoknow said:
-pi - (pi/3) < x - pi/3 < pi - (pi/3)

-4pi < x-(pi/3) < 2pi/3and I know that -5pi/4 and pi/4 fit the new range as a result of the translation pi/3 I just don't know what to do with them. Can someone please help?That is so far what I have got I do not know where to proceed from
 
  • #3
oh sorry that's a typo its actually -pi < x < +pi and root(2)/2
 
  • #4
Can you solve sin(u) > ##\sqrt{2}/2##? There are lots of intervals that satisfy this inequality. Once you get that, then solve for x, where u = x - ##\pi/3##.
 
  • #5
Is there a way to solve this without the use of a graph though?
 
  • #6
needingtoknow said:
Is there a way to solve this without the use of a graph though?
I suppose, but why would you not want to use a graph? That's probably the simplest way to proceed.
 

FAQ: Trignometric inequality problem

What is a trigonometric inequality problem?

A trigonometric inequality problem involves solving an inequality that contains trigonometric functions, such as sine, cosine, and tangent. These problems often require the use of trigonometric identities and properties to find the solutions.

How do I solve a trigonometric inequality problem?

To solve a trigonometric inequality problem, you can follow these steps:

  1. Isolate the trigonometric function on one side of the inequality.
  2. Use trigonometric identities and properties to simplify the expression.
  3. Graph the trigonometric function to determine the intervals where the function is positive or negative.
  4. Use the graph and the intervals to write the solution set for the inequality.

What are some common trigonometric identities and properties used in solving inequalities?

Some common trigonometric identities and properties used in solving inequalities include the Pythagorean identities, the sum and difference identities, and the double angle identities. These can be used to simplify expressions and manipulate inequalities to find solutions.

Can I use a calculator to solve trigonometric inequality problems?

While a calculator can be a helpful tool in solving trigonometric inequality problems, it is important to have a solid understanding of trigonometric functions and their properties in order to correctly use the calculator and interpret the results.

What are some real-life applications of trigonometric inequality problems?

Trigonometric inequality problems have various real-life applications, such as in physics, engineering, and architecture. For example, in physics, trigonometric inequalities can be used to model and solve problems related to forces and motion. In architecture, they can be used to determine the stability and strength of structures.

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