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Find the least value of 2 sin^(2) theta+...

Find the least value of `2 sin^(2) theta+ 3 cos^(2) theta`.

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To find the least value of the expression \( y = 2 \sin^2 \theta + 3 \cos^2 \theta \), we can follow these steps: ### Step 1: Rewrite the expression We start with the expression: \[ y = 2 \sin^2 \theta + 3 \cos^2 \theta \] Using the Pythagorean identity, we know that: \[ \sin^2 \theta + \cos^2 \theta = 1 \] We can express \( \sin^2 \theta \) in terms of \( \cos^2 \theta \): \[ \sin^2 \theta = 1 - \cos^2 \theta \] Substituting this into the expression for \( y \): \[ y = 2(1 - \cos^2 \theta) + 3 \cos^2 \theta \] ### Step 2: Simplify the expression Now, we simplify the expression: \[ y = 2 - 2 \cos^2 \theta + 3 \cos^2 \theta \] Combining like terms gives: \[ y = 2 + \cos^2 \theta \] ### Step 3: Determine the range of \( \cos^2 \theta \) The value of \( \cos^2 \theta \) ranges from 0 to 1, since \( \cos^2 \theta \) is always non-negative and cannot exceed 1. ### Step 4: Find the minimum value of \( y \) To find the least value of \( y \), we consider the minimum value of \( \cos^2 \theta \): \[ \text{Minimum value of } \cos^2 \theta = 0 \] Substituting this into the expression for \( y \): \[ y_{\text{min}} = 2 + 0 = 2 \] ### Conclusion Thus, the least value of \( 2 \sin^2 \theta + 3 \cos^2 \theta \) is: \[ \boxed{2} \]
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