I am not sure if I am fully understanding how to solve this, but I think that, since the since g(x)=cos(x) and g(x)=x^3 are continuous everywhere, the function f(x)=cos(x)−x^3 must also be continuous everywhere, and therefore, according to the Intermediate Value Theorem, cos(x)=x^3 must have a solution. However, I'm not sure if that's true. How can I show that cos(x)=x^3 has a solution?

waldo7852p

waldo7852p

Answered question

2022-09-21

I think that, since the since g ( x ) = cos ( x ) and g ( x ) = x 3 are continuous everywhere, the function f ( x ) = cos ( x ) x 3 must also be continuous everywhere, and therefore, according to the Intermediate Value Theorem, cos ( x ) = x 3 must have a solution. However, I'm not sure if that's true.
How can I show that cos ( x ) = x 3 has a solution?

Answer & Explanation

Jane Acosta

Jane Acosta

Beginner2022-09-22Added 14 answers

Because f ( x ) is continuous and hence satisfies the IVT, AND it is negative at say x = π, AND it is positive at say x = 0, we know that between those two x values f ( x ) = 0.
waldo7852p

waldo7852p

Beginner2022-09-23Added 2 answers

By f ( x ) you mean cos ( x ) x 3 i guess

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