Hitunglah nilai A.Sin 165° + Sin 75° B.Cos 105° Sin 75°

jawab

a)
sin 165 + sin 75 = 2 sin 1/2(165+75) cos 1/2 (165-75)
= 2 sin 120 cos 45
= 2(1/2 √3)(1/2 √2)
= 1/2 √6

b)
cos 105 sin 75 = 1/2 ( 2 cos 105 sin 75)
= 1/2 { sin (105+75) - sin (105-75)}
= 1/2{ sin 180 - sin 30)
= 1/2 (0 - 1/2)
= - 1/4