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Cosine Inequality Challenge (Posted on 2024-06-30)

Find the domain of x∈[0,2π] so that cos(5x)≤cos(3x).

No Solution Yet Submitted by Danish Ahmed Khan

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Solution

| Comment 1 of 2

The functions can be equal if 5x = 3x + 2kπ

2x = 2kπ, x = kπ

The functions can be equal if 5x = -3x + 2kπ

8x = 2kπ, x = kπ/4 (which includes the above)

The two functions are equal at x = k*π/4

The condition is True for:

0 < x < π/4

π/2 < x < 3π/4

5π/4 < x < 3π/2

7π/4 < x < 2π

Desmos:

https://www.desmos.com/calculator/grfmiwn7cz

Posted by Larry on 2024-06-30 14:18:14

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