tentukan nilai dari cos2 phi/4-cos2 phi/6+sin4 phi/6+sin4 phi/3

Cos2π/4 - cos2π/6 + sin4π/6 +sin 4π/3
= 3cos2π-2cos2π/12 + sin4π+2sin4π/6
= cos2π/12 + 3sin4π/6
= cos2π/12 + 6sin2πcos2π/6 (π=180°)
= cos360/12 + 6sin360cos360/6
= 1/12 + 0
= 1/12