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

If x = a cos³ θ and y = b sin³ θ, then $\Big(\dfrac{x}{a}\Big)^{\dfrac{2}{3}} + \Big(\dfrac{y}{b}\Big)^{\dfrac{2}{3}}$ is equal to :

1. a

2. b

3. 1

4. 2

The expression equivalent to sec x, is :

1. $\tan x + \dfrac{\sin x}{\sec x}$

2. $\cos x + \dfrac{\tan x}{\cos x}$

3. cos x + tan x sin x

4. tan x − cos x sin x

$\dfrac{\sin^4 A − \cos^4 A}{1 − \sin^2 A}$ is equal to :

1. cot² A − 1

2. tan² A − 1

3. 1 − cot² A

4. 1 − tan² A