If △ABC is right angled at C, then the value of cos (A + B) is

1. 0

2. 1

3. $\dfrac{1}{2}$

4. $\dfrac{\sqrt{3}}{2}$

In the adjoining figure, ABC is a right triangle right angled at B. If AB = 10 cm and ∠C = 30°, then the length of the side BC is

1. $\dfrac{10}{\sqrt{3}}$ cm

2. $10\sqrt{3}$ cm

3. 20 cm

4. 5 cm

Consider the following two statements.

Statement 1: sin 18° - cos 72° = 0.

Statement 2: sin θ = cos (90° - θ).

Which of the following is valid?

1. Both the statements are true.

2. Both the statements are false.

3. Statement 1 is true, and Statement 2 is false.

4. Statement 1 is false, and Statement 2 is true.

Assertion (A): tan 30° + sec 30° = cot 30°.

Reason (R): sec θ = $\dfrac{\text{cosec θ}}{\text{cot θ}}$

1. Assertion (A) is true, Reason (R) is false.

2. Assertion (A) is false, Reason (R) is true.

3. Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct reason for Assertion (A).

4. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct reason (or explanation) for Assertion (A).