The expression equivalent to sec² θ + cosec² θ is :

1. sec² θ · cosec² θ

2. tan² θ + cot² θ

3. $\dfrac{1}{\sec^2 θ \times \cosec^2 θ}$

4. 2 sec² θ + 1

sec² θ + cosec² θ

$\Rightarrow \dfrac{1}{\cos^2 \theta} + \dfrac{1}{\sin^2 \theta} \\[1em] \Rightarrow \dfrac{\sin^2 \theta + \cos^2 \theta}{\cos^2 \theta\sin^2 \theta} \\[1em] \Rightarrow \dfrac{1}{\cos^2 \theta\sin^2 \theta} \\[1em] \Rightarrow \sec^2 \theta (\cosec^2 \theta)$

Hence, option 1 is the correct option.