`costheta=(a^(2)+b^(2))/(2ab)`, where a and b are two distinct numbers such that `ab gt 0`.

Explanation

To solve the problem, we need to analyze the expression given:

\[ \cos \theta = \frac{a^2 + b^2}{2ab} \]

where \( a \) and \( b \) are two distinct positive numbers such that \( ab > 0 \).

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