1.
Let P=∏k=2n(1−1k2)P = \prod_{k=2}^{n} \left(1 - \frac{1}{k^2}\right). If lim⁡n→∞P\lim_{n \to \infty} P can be expressed as lowest rational ab\frac{a}{b}, then the value of (a+b)(a + b) is