求解答求学霸!必采纳!
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2014-08-10
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tan(a+π/5)=tan(α+β-b+π/5)
=tan(α+β-(β-π/5))
=[tan(α+β)-tan(β-π/5)]/[1+tan(α+β)*tan(β-π/5)]
=(2/5-1/5)/(1+2/5*1/5) 分子分母各乘20
= (2/5-1/5)*20/(1+2/5*1/5)*20
=(8-4)/(20+2)
=4/22
=tan(α+β-(β-π/5))
=[tan(α+β)-tan(β-π/5)]/[1+tan(α+β)*tan(β-π/5)]
=(2/5-1/5)/(1+2/5*1/5) 分子分母各乘20
= (2/5-1/5)*20/(1+2/5*1/5)*20
=(8-4)/(20+2)
=4/22
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