Mark the Correct alternative in the following:
The value of sin 78^o – sin 66^o – sin 42^o + sin 6^o is

Question

Mark the Correct alternative in the following: The value of sin 78 o – sin 66 o – sin 42 o + sin 6 o is

Philoid · Accepted Answer

sin 78° - sin 66° - sin 42° + sin 6°

= (sin 78° - sin 42°) – (sin 66° - sin 6°)

= 2cos 60° sin 18° - 2cos 36° sin 30°

= 2 ⋅ 1/2 ⋅ sin 18° - 2 ⋅ 1/2 ⋅ cos 36°

= sin 18° - cos 36°

=

= - 1/2 (Ans)

Mark the Correct alternative in the following:The value of sin 78o – sin 66o – sin 42o + sin 6o is