(tan x+tan y)/(tan x-tan y)=sin(x+y)/sin(x-y)
參考答案:(tan x+tan y)/(tan x-tan y)
=(sinx/cosx+siny/cosy)/(sinx/cosx-siny/cosy)
=(sinxcosy+sinycosx/cosxcosy)/(sinxcosy-sinycosx/cosxcosy)
=sin(x+y)/sin(x-y)
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(tan x+tan y)/(tan x-tan y)=sin(x+y)/sin(x-y)
參考答案:(tan x+tan y)/(tan x-tan y)
=(sinx/cosx+siny/cosy)/(sinx/cosx-siny/cosy)
=(sinxcosy+sinycosx/cosxcosy)/(sinxcosy-sinycosx/cosxcosy)
=sin(x+y)/sin(x-y)