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if tanx = -1/3 and cosx>0
what is:
sin2x
cos2x
tan2x
 Mar 7, 2014
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Hello mathao21!
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sinx=(-1/3)/(sqrt(1+(-1/3)^2))

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cosx=1/(sqrt(1+(-1/3)^2))

And now, for sin 2x:
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sin2x=2*((-1/sqrt(10))*(3/sqrt(10)))

...for cos 2x:
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cos2x=1-2*(-1/sqrt(10))^2

...for tan 2x:
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tan2x=(2*(-1/3))/(1-((-1/3)^2)))

To sum up:
If tanx=-1/3 and cosx>0 then:
[list]
  • sin2x= -3/5[/*:m]
  • cos2x= 4/5[/*:m]
  • tan2x= -3/4[/*:m][/list:u]

    Have a nice day!
    Dms
  •  Mar 7, 2014

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