1-tanα/1+tanα=1-2sinαcosα - 知识问答

1-tanα/1+tanα=1-2sinαcosα/cos^2α-sin^2α求证啊

1个回答

1-sinα/cosα sin^2α+cos^2α-2sinαcosα
------------ = --------------------------
1+sinα/cosα cos^2α-sin^2α
1-sinα/cosα (sinα-cosα)^2
------------ = --------------------
1+sinα/cosα cos^2α-sin^2α
cosα-sinα (cosα-sinα)^2
------------ = --------------------
cosα+sinα (cosα-sinα)(cosα+sinα)
cosα-sinα (cosα-sinα)
------------ = --------------------
cosα+sinα (cosα+sinα)

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