tunjukkan bahwa cotg 120° = cos 120°/sin 120°

→ cot120 = -1/√3
→ cos120 = -1/2
→ sin120 = 1/2√3

-1/√3 = -1/2 / 1/2√3
-1/√3 = -1/√3

Menggunaka Identitas Trigonom :
→ 120˚ = x
→ [ cosx / sinx = cotx ]

cotx = cosx / sinx
cotx = cotx
cos120 = cos120