y=r sin ∅
\(1=r sin \frac{3 \pi }{4} =rsin( \pi - \frac{ \pi }{4} )=r sin \frac{ \pi }{4} = \frac{r}{ \sqrt{2} } ,r= \sqrt{2}\)
\(x=r cos \frac{3 \pi }{4} =rcos( \pi - \frac{pi}{4} )=-rcos \frac{ \pi }{4} = \sqrt{2} * \frac{1}{ \sqrt{2} } =-1\)
so co-ordinates are (-1,1)
