The value of cot81° – cot63° – cot27° + cot9° is

• Answer: 4
  
  (cot 81° + cot 9°) - (cot 63° + cot 27°)
  (cos 81°sin9° + sin81°cos9°)/(sin9°sin81°) - (cos 63°sin 27° + sin 63°cos 27°)/(sin 27°sin 63°)
  sin 90°/(sin9°sin81°) - sin 90°/(sin27°sin63°)
  2/(cos72°) - 2/(cos36°)
  8/(√5 - 1) - 8/(√5 + 1)
  4
• 6 years agoHelpfull: Yes(0) No(0)