已知(1+tanα)/(1-tanα)=2010,求(1/cos2α)+tan2α的值
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已知(1+tanα)/(1-tanα)=2010,求(1/cos2α)+tan2α的值
已知(1+tanα)/(1-tanα)=2010,求(1/cos2α)+tan2α的值
已知(1+tanα)/(1-tanα)=2010,求(1/cos2α)+tan2α的值
(1+tanα)/(1-tanα)=2010,anα=2009/2011,
(1/cos2α)+tan2α=1/(2cos²α-1)+2anα/(1-tan²α)=1/[2/(1+tan²α)-1]+2anα/(1-tan²α)
=(1+tan²α)/(1-tan²α)+2anα/(1-tan²α)=(1+tanα)²/(1-tan²α)=(1+2009/2011)²/[1-(2009/2011)²]
=2010
或者:
(1/cos2α)+tan2α=1/(2cos²α-1)+2anα/(1-tan²α)=1/[2/(1+tan²α)-1]+2anα/(1-tan²α)
=(1+tan²α)/(1-tan²α)+2anα/(1-tan²α)=(1+tanα)²/(1-tan²α)=(1+tanα)/(1-tanα)=2010
tanα=2009/2011,令sinα=2009x,cosα=2011x,则(1/cos2α)+tan2α=(1+sin2α)/cos2α=(1+2sinα*cosα)/(cos²α-sin²α)=(sinα+cosα)²/(cos²α-sin²α)=(sinα+cosα)/(cosα-sinα)=4020x/2x=2010
222222 bbbbbbb 2010
(1/cos2α)+tan2α=1/(cos²α-sin²α)+2tanα/(1-tan²α)
=(cos²α+sin²α)/(cos²α-sin²α)+2tanα/(1-tan²α)
=(1+tan²α)/(1-tan²α)+2tanα/(1-tan²α)
=(1...
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(1/cos2α)+tan2α=1/(cos²α-sin²α)+2tanα/(1-tan²α)
=(cos²α+sin²α)/(cos²α-sin²α)+2tanα/(1-tan²α)
=(1+tan²α)/(1-tan²α)+2tanα/(1-tan²α)
=(1+tanα)²/[(1+tanα)*(1-tanα)
]=(1+tanα)/(1-tanα)=2010
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