Tan(A+45度)+Tan(A-45度)=2Tan2A

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Tan(A+45度)+Tan(A-45度)=2Tan2ATan(A+45度)+Tan(A-45度)=2Tan2ATan(A+45度)+Tan(A-45度)=2Tan2ATan(A+45)+Tan(A-

Tan(A+45度)+Tan(A-45度)=2Tan2A
Tan(A+45度)+Tan(A-45度)=2Tan2A

Tan(A+45度)+Tan(A-45度)=2Tan2A
Tan(A+45)+Tan(A-45)
=(tanA+1)/(1-tanA)+(tanA-1)/(1+tanA)
=(tanA+1)^2/(1-tan^2A)+(tanA-1)^2/(tan^2A-1)
=[(tanA+1)^2-(tanA-1)^2]/(1-tan^2A)
=4tanA/(1-tan^2A)
=2tan2A

tan(A+45度)=[tanA+tan(45度)]/[1-tanA*tan(45度)]
再根据公式化简就OK了