\(\frac{3 \pi }{4} * \frac{180degrees}{ \pi } = 135 degrees\).
Drawing a reference triangle, this is 45 degrees in the second quadrant.
See attached.
Sine theta will be opposite/hypotenuse
\(= \frac{1}{ \sqrt{2} } * \frac{ \sqrt{2} }{ \sqrt{2} } = \frac{ \sqrt{2} }{2}\)
Cosine will be adjacent/hypotenuse
\(\frac{-1}{ \sqrt{2} } * \frac{ \sqrt{2} }{ \sqrt{2} } = \frac{- \sqrt{2} }{2}\)
Tangent will be opposite/adjacent
\(\frac{1}{-1}=-1\)
