tan=3,怎么算sin平方a减cos平方a
tan=3,怎么算sin平方a减cos平方a 已知tanα=3 而:sin^2 α-cos^2 α=(sin^2 α-cos^2 α)/1 =(sin^2 α-cos^2 α)/(sin^2 α+cos^2 α) =[(sin^2 α/cos^2 α)-1]/[(sin^2 α/cos^2 α)+1]【分子分母同除以cos^2 α】 =(tan^2 α-1)/(tan^2 α+1) =(3^2-1)/(3^2+1) =4/5
请问:是tana=3吗?如是方可解。
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