Find all solutions in the interval [0, 2] for the equation 0 < tan(x) sec(x) < 1

To solve the inequality 0 < tan(x) sec(x) < 1, we first need to understand the expressions involved. Recall that sec(x) = 1/cos(x) and tan(x) = sin(x)/cos(x). Thus, we can rewrite the product:

tan(x) sec(x) = tan(x) * (1/cos(x)) = (sin(x)/cos(x)) * (1/cos(x)) = sin(x) / cos^2(x).

Now, we want to find the solutions to the inequality:

  • 1. First part: 0 < sin(x) / cos^2(x)

This means that sin(x) > 0 and cos^2(x) > 0. Since cos^2(x) > 0 for all x except where cos(x) = 0 (i.e., at odd multiples of π/2), we need to focus on where sin(x) > 0.

  • 2. Second part: sin(x) / cos^2(x) < 1

Rearranging gives:

sin(x) < cos^2(x).

To find solutions for this inequality, we can analyze the graphs of sin(x) and cos^2(x) or solve it algebraically. However, since we are looking for solutions in the interval [0, 2], let’s check critical points:

  • x = 0: sin(0) = 0, cos(0) = 1, thus 0 < 1.
  • x = π/2: sin(π/2) = 1, cos(π/2) = 0, thus undefined.
  • x = π: sin(π) = 0, thus 0 < 1.
  • x = 3π/2: sin(3π/2) = -1, thus not in the solution set.
  • x = 2: sin(2) > 0, cos(2) > 0.

Next, in intervals (0, π), (π, 2), check where sin(x) < cos^2(x) holds true:

From testing values, we find:

  • On (0, π/2), both conditions are satisfied.
  • On (π/2, π), while sin(x) is positive, the value exceeds cos^2(x).
  • On (π, 2), the sine is ≤0, hence not applicable.

In conclusion, the solutions in the interval are:

  • x ∈ (0, π/2)

Thus, the final result is:

  • x ∈ (0, π/2)

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