tentukan nilai dari sin 3n/4 sin n/4 +cos 3n/4 cos n/4 catatan n =180

Bab Trigonometri
Matematika SMA Kelas X

sin 3π/4 . sin π/4 + cos 3π/4 . cos π/4
= cos 3π/4 . cos π/4 + sin 3π/4 . sin π/4
= cos (3π/4 - π/4)
= cos 2π/4
= cos π/2
= 0