cos2x等于多少tanx

姜秀爽2230cos2x=1/3,则tanx=? -
廖学泥18050849599 ______ 由题意知 2x=60度 所以x=30° 则tan30°=三分之根号三

姜秀爽2230若tanx=2则cos2x等于? -
廖学泥18050849599 ______ cos2x=cos²x-sin²x=(cos²x-sin²x)/(cos²x+sin²x)=(1-tan²x)/(1+tan²x)=-3/5

姜秀爽2230已知cos2x=5/13(3∏<x<2∏)求tanx -
廖学泥18050849599 ______ 应该是这个吧: 3π/2<x<2π tanx<0 cos2x =(1-tan方x)/(1+tan方x)=5/13 13-13tan方x=5+5tan方x 18tan方x=8 tan方x=4/9 所以 tanx=-2/3

姜秀爽2230cos^2x为什么等于(1 - tan^2x)/(1+tan^x) -
廖学泥18050849599 ______ cos2x =(1-tan^2x)/(1+tan^2x) , 你写错了.这公式叫做万能公式.证明:cos2x = cos^2x - sin^2x= (cos^2x - sin^2x)/ ( cos^2x +sin^2x) 注意:cos^2x +sin^2x =1= (1-tan^2x)/(1+tan^2x) 分子、分母同除cos^2x,

姜秀爽2230cos2x=(1 - tan平方x)/(1+tan平方x) 请问这个式子是怎么推出来的. -
廖学泥18050849599 ______[答案] (1-tan平方x)/(1+tan平方x) =(1-sin²x/cos²x)/(1+sin²x/cos²x) =(cos²x-sin²x)/(cos²x+sin²x) =cos2x 得证

姜秀爽2230Sinx等于2COSx则cos2x等于多少 -
廖学泥18050849599 ______[答案] sinx=2cosx,则tanx=sinx/cosx=2 cos2x=cos²x-sin²x=[cos²x-sin²x]/[cos²x+sin²x]=[1-tan²x]/[1+tan²x]=-3/5

姜秀爽22301 - cos2x=多少? 求关于sin cos tan arctan等等之间转化的所有公式,以前学的全忘了 哎 -
廖学泥18050849599 ______ 1-cos2x=2sin^2x sin^2x+cos^2x=1 sinx/cosx=tanx

姜秀爽2230tan(X+∏/4)=2求cos2X -
廖学泥18050849599 ______ tan(x+π/4)=2tanx/(1-tanx)=-1/2 ∴ tanx=-1. ∴tanx=1 cos2x=cosx-sinx=1-tanx=0 或者,tanx=-1. 得x=kπ-π/4 ∴ 2x=2kπ-π/2 所以cos2x=0 非常详细了同学,给最佳吧 满意请采纳

姜秀爽2230已知tan(x+π/4)=2,则cos2x=? -
廖学泥18050849599 ______[答案] tan(x+π/4) = (tanx+tanπ/4)/(1-tanxtanπ/4) = (tanx+1)/(1-tanx) = 2tanx+1 = 2-2tanx3tanx = 1tanx=1/3cosx = ±1/根号(1+tan^2x) = ±1/根号(1+1/9) = ± 3/根号10cos2x = 2cos^2x - 1 = 2*(±3/根号10)^2 - ...

姜秀爽2230已知tan(x+π/4)=2,则cos2x=? -
廖学泥18050849599 ______ tan(x+π/4) = (tanx+tanπ/4)/(1-tanxtanπ/4) = (tanx+1)/(1-tanx) = 2 tanx+1 = 2-2tanx3tanx = 1 tanx=1/3 cosx = ±1/根号(1+tan^2x) = ±1/根号(1+1/9) = ± 3/根号10 cos2x = 2cos^2x - 1 = 2*(±3/根号10)^2 - 1 = 18/10 - 1 = 4/5