Sin(x)= -2/(5^0.5), 3pi/2<x<2pi

then i have that cos(x)=+-(1-(-2/(5^0.5))^0.5=+-1/(5^0.5)

and tan(x)=((-2/(5^0.5))/(1/(5^0.5)=2

but what is the exaktly valus of this expression: cos(2x-3pi/4)?

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- Jan 10th 2011, 07:27 AM #1

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## Value of cos(2x-3pi/4).

Sin(x)= -2/(5^0.5), 3pi/2<x<2pi

then i have that cos(x)=+-(1-(-2/(5^0.5))^0.5=+-1/(5^0.5)

and tan(x)=((-2/(5^0.5))/(1/(5^0.5)=2

but what is the exaktly valus of this expression: cos(2x-3pi/4)?

- Jan 10th 2011, 01:31 PM #2