Given x = cos(θ), the equation x² - 3x + 2 = 0, find the value of θ.

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TNPSC Group 1 Services Prelims 2010 Official Paper
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  1. 1
  2. 0
  3. -1
  4. π 

Answer (Detailed Solution Below)

Option 2 : 0
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Given:

x = cos(θ)

The equation: x² - 3x + 2 = 0

Calculation:

Factor the quadratic equation:

(x - 1)(x - 2) = 0

So, x = 1 or x = 2

Now, since x = cos(θ):

For x = 1: cos(θ) = 1 ⇒ θ = 0° (or 0 radians)

For x = 2: cos(θ) = 2 ⇒ This is not possible because cosine values are between -1 and 1.

∴ The only valid solution is θ = 0° (or 0 radians).

Answer: B) 0

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