Answers

2014-11-02T23:36:03+05:30
Cot (A+B) = (CotACotB-1)/(CotA + CotB )
We know......Cot(45)=1
so,          1=
(CotACotB-1)/(CotA + CotB )
          
CotACotB-1)=  (CotA + CotB )
          
CotACotB-cotA-cotB=1
adding 1 to both sides.....we get
  
(cotA-1)(cotB-1)=2......proved


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