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

- Joined
- Dec 2010
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- 52

## 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)?

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