hitunglah a) 8 cos 82,5° dikali sin 37,5° b) 2 sin 52,5° dikali sin 7,5° c) cos 5/12 Π - cos 1/2Π kak tolong bantu yang tau yaaa plisss Π=phi

Rumus
2.cosa.sinb = sin(a+b) - sin(a-b)

8 cos 82,5° sin 37,5°
= 4(2.cos 82,5° sin 37,5°)
= 4(sin(82,5+37,5) - sin(82,5-37,5)
= 4(sin120 - sin45)
= 4( 1/2 akar3 - 1/2 akar2)
= 2 akar3 - 2 akar2

Rumus
-2.sina.sinb = cos(a+b) - cos(a-b)

2 sin 52,5° sin 7,5°
= -(cos(52,5+7,5) - cos(52,5-7,5))
= -(cos60 - cos 45)
= -1/2 + 1/2 akar 2

Rumus
cosa - cosb = -2.sin(a+b)/2 . sin(a-b)/2

5/12 Π = 75°
1/12Π = 15°

cos 5/12 Π - cos 1/12Π
= cos 75 - cos 15
= -2.sin(75+15)/2 . sin(75-15)/2
= -2.sin45.-sin30
= 2. 1/2 akar2. 1/2
= 1/2 akar2