※ 引述《kusorz (^~^)》之銘言：
: 試求tan^-1(125)+tan^-1(0.008)=?
-1
令 A = tan (125) , 0 < A < π/2
-1
B = tan (0.008) , 0 < B < π/2
則 tanA = 125 , tanB = 0.008
0 < A + B < π
tan(A + B)
tanA + tanB
= ------------------
1 - (tanA)(tanB)
125 + 0.008
= ------------------
1 - (125)(0.008)
125.008 125.008
= --------- = --------- = ∞
1 - 1 0
-1 -1 π
tan (125) + tan (0.008) = A + B = ---
2
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