Solution to Trig Inequality in [0,-1]

In summary, the conversation is discussing how to prove that the equation x=sin(piex) + cos(piex) has a solution in the interval [0,-1]. One person suggests changing the equation into f(x)=x-sin(pi*x)-cos(pi*x)=0 and looking at the signs of f(0) and f(1). Another person points out that the initial statement of 0 <= sin(piex) + cos(piex) <= 1 is not true.
  • #1
skateza
45
0

Homework Statement


Show that x=sin(piex) + cos(piex) has a solution in [0,-1]

The Attempt at a Solution



well i know that 0 <= x <= 1
therefore 0 <= sin(piex) + cos(piex) <= 1

But how do i go about solving this inequality?
 
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  • #2
You don't go about solving it. You just prove it has a solution. Change the equation into f(x)=x-sin(pi*x)-cos(pi*x)=0. f(0)=(-1). f(1)=2. Does that suggest anything?
 
  • #3
skateza said:

Homework Statement


Show that x=sin(piex) + cos(piex) has a solution in [0,-1]

The Attempt at a Solution



well i know that 0 <= x <= 1
therefore 0 <= sin(piex) + cos(piex) <= 1

But how do i go about solving this inequality?
That certainly is NOT true! What is sin(pi)+ cos(pi)? Look at the signs of sin(pix)+ cos(pix)- x at 0 and 1.
 

What is a trigonometric inequality?

A trigonometric inequality is an inequality that involves trigonometric functions, such as sine, cosine, and tangent. These inequalities can be solved using algebraic techniques and the properties of trigonometric functions.

What is the solution to a trigonometric inequality in the interval [0,-1]?

The solution to a trigonometric inequality in the interval [0,-1] is the set of all values of the variable that satisfy the inequality. This means that any value within the interval that makes the inequality true is part of the solution set.

How do I solve a trigonometric inequality in the interval [0,-1]?

To solve a trigonometric inequality in the interval [0,-1], you can use algebraic techniques such as factoring and the properties of trigonometric functions. You will also need to use knowledge of the unit circle and the periodic nature of trigonometric functions.

Why is it important to find the solution to a trigonometric inequality in the interval [0,-1]?

Finding the solution to a trigonometric inequality in the interval [0,-1] can help you determine the range of values for a variable that will make the inequality true. This can be useful in various applications, such as optimizing a function or solving real-world problems involving angles or triangles.

Can a trigonometric inequality in the interval [0,-1] have multiple solutions?

Yes, a trigonometric inequality in the interval [0,-1] can have multiple solutions. This is because trigonometric functions are periodic and have an infinite number of solutions. For example, the inequality sinx > 0 in the interval [0,-1] has infinitely many solutions, as sine is positive in all quadrants of the unit circle.

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