已知tanx=2,求下列各式的值 1) (cosx+sinx)/(cosx-sinx) 2) sinxcosx-1 3) 2+sinxcosx-cos²x
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![已知tanx=2,求下列各式的值 1) (cosx+sinx)/(cosx-sinx) 2) sinxcosx-1 3) 2+sinxcosx-cos²x](/uploads/image/z/1042191-63-1.jpg?t=%E5%B7%B2%E7%9F%A5tanx%3D2%2C%E6%B1%82%E4%B8%8B%E5%88%97%E5%90%84%E5%BC%8F%E7%9A%84%E5%80%BC+1%EF%BC%89+%EF%BC%88cosx%2Bsinx%EF%BC%89%2F%28cosx-sinx%29+2%EF%BC%89+sinxcosx-1+3%EF%BC%89+2%2Bsinxcosx-cos%26%23178%3Bx)
已知tanx=2,求下列各式的值 1) (cosx+sinx)/(cosx-sinx) 2) sinxcosx-1 3) 2+sinxcosx-cos²x
已知tanx=2,求下列各式的值 1) (cosx+sinx)/(cosx-sinx) 2) sinxcosx-1 3) 2+sinxcosx-cos²x
已知tanx=2,求下列各式的值 1) (cosx+sinx)/(cosx-sinx) 2) sinxcosx-1 3) 2+sinxcosx-cos²x
(1)(cosx+sinx)/(cosx-sinx)=(1+tanx)/(1-tanx)=(1+2)/(1-2)=-3
(2)sinxcosx-1=sinxcosx/[(sinx)^2+(cosx)^2]-1=tanx/[1+(tanx)^2]-1=2/5-1=-3/5
(3)2+sinxcosx-(cosx)^2=2+[sinxcosx-(cosx)^2]/[(sinx)^2+(cosx)^2]
=2+[tanx-1]/[(tanx)^2+1]=2+(2-1)/(4+1)=2+1/5=11/5
答案:1)-3 2)-3/5 3)11/5
1)-3
2)-3
3)11