Question

1. The value of sin 18° sin 42° sin 78° cosec 54° is 1 a) 1 b) 2 C) 4 d) 16 ​

Answer 1

Answer:

b is correct answer I think friend

Answer 2

Note:-

Sin(60°+Ø).SinØ.Sin(60°-Ø)=(Sin3Ø)/4 and SinØ.CosecØ = 1.

AQ,

Sin18°.Sin42°.Sin78°.Cosec54°

looking carefully, Ø=18°

= {Sin(60+18°).Sin18°.Sin(60°-18°)}.Cosec54°

= Sin{3(18°)}.Cosec54°

= {(Sin54°)/4}.Cosec54°

= (Sin54°.Cosec54°)/4

= 1/4.

Hence the answer will be option C.