Nilai dariCos195°+cos465°+cos330°=

TriGonoMetRi

cos a + cos b = 2 cos (a+b)/2 cos (a-b)/2

••
cos 195 + cos 465 + cos 330
= 2 cos 330 cos (-135) + cos 330
= 2 cos 30° (- cos 45°) + cos 30°
= 2 (1/2 √3)(-1/2 √2) + (1/2 √3)
= (1/2 √3) (1 - √2)
= (1/2)(√3 - √6) ✔