i want to explain the solution in this question ..

I worked a red line on the steps that I did not understood it

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- Dec 7th 2009, 12:24 PMr-soyi want to explain the solution in this questioni want to explain the solution in this question ..

I worked a red line on the steps that I did not understood it - Dec 7th 2009, 01:03 PMmasters
- Dec 7th 2009, 01:42 PMr-soy
Hi but from where we get

$\displaystyle

\cos \frac{2\pi}{2}

$

in step 2 - Dec 7th 2009, 01:51 PMmasters
- Dec 8th 2009, 06:27 AMr-soy
thanks so much

- Dec 8th 2009, 06:47 AMr-soy
ok who u can know

cos(3pi/2)=cos(270)=0

sin(3pi/2)=sin(270)= -1

from where i can get 0 and -1 ?

give me a way to finid them - Dec 8th 2009, 08:22 AMmasters
On your unit circle, at an angle of 270 deg or 3pi/2, the coordinates of the intersection of the circle with the negative side of the y-axis is (0, -1). Cosine is defined as x/r, where x = x-coordinate of the circle and r = the radius.

$\displaystyle \cos 270=\frac{x}{r}=\frac{-1}{1}=-1$

Similarly, sine 270 is defined as y/r.

$\displaystyle \sin 270=\frac{y}{r}=\frac{0}{1}=0$

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