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2012-06-13 19:02:32

• tan(A+π/2) =tan(A+B- (B-π/2) 
  =( tan(A+B) - tan(B-π/2))/(1+tan(A+B)* tan(B-π/2))
  =(2/5-1/4)/(1+2/5*1/4) = 3/22;
  tanA = -22/3;
  tan(π/4+A) = (1+tan(A))/(1- tan(A)) = (1-22/3)/(1+22/3)
  = -19/25

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  m***

  2012-06-13 19:02:32

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2012-06-13 18:55:04

• tan(π/2 + A) =tan[(A+B)-(B-π/2)]
  =[tan(A+B)-tan(B-π/2)]/[1+tan(A+B)*tan(B-π/2)]
  =3/22
  tan(π/4+A)=tan[(π/2+A)-π/4]
  =[tan(π/2+A)-tan(π/4)]/[1+tan(π/2+A)*tan(π/4)]
  =[tan(π/2+A)-1]/[1+tan(π/2+A)]
  =-19/25

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  l***

  2012-06-13 18:55:04

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