Question

In the following questions, two statements (i) and (ii) are given. Choose the valid statement.

(i) If θ = 15° then `(sin 3θ)/(cos 4θ) = sqrt(2)`

(ii) cot 20° cot 40° cot 50° cot 70° = 2

विकल्प

• Only (i)

• Only (ii)

• Both (i) and (ii)

• Neither (i) nor (ii)

Answer 1

Only (i)

Explanation:

(i) With θ = 15°. 

`(sin 3θ)/(cos 4θ)` 

= `(sin 45^circ)/(cos 60^circ)` 

= `(sqrt(2)/2)/(1/2)` 

= `sqrt(2)`

(ii) cot 20° · cot 40° · cot 50° · cot 70°

= cot 20° · cot 40° · tan 40° · tan 20° 

= 1 (not 2) 

So, (ii) is false.