化简求值;(1-sin80°)/cos80°
1个回答
2011-04-04
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1-sin80°)/cos80°
=(1-sin2*40°)/(cos2*40°)
=(1-2sin40°cos40°)/(2cos240°-1)
=(sin240°+cos240°-2sin40°cos40°)/(2cos240°-sin240°-cos240°)
=(cos40°-sin40°)2/(cos240°-sin240°)
=(cos40°-sin40°)2/(cos40°-sin40°)(cos40°+sin40°)
=(cos40°-sin40°)/(cos40°+sin40°)
=(1-sin2*40°)/(cos2*40°)
=(1-2sin40°cos40°)/(2cos240°-1)
=(sin240°+cos240°-2sin40°cos40°)/(2cos240°-sin240°-cos240°)
=(cos40°-sin40°)2/(cos240°-sin240°)
=(cos40°-sin40°)2/(cos40°-sin40°)(cos40°+sin40°)
=(cos40°-sin40°)/(cos40°+sin40°)
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