[tex] \frac{7 \pi}{6} = \frac{7*180}{6} = 7*30 = 210 [/tex]
210 we can write it as 210 = 180 + 30.
So 210 has a reference angle of 30 degree in third quadrant.
So x co-ordinate of terminal point is cos(210) = [tex] \frac{- \sqrt{3} }{2} [/tex]
y co-ordinate of terminal point is sin(210) = [tex] \frac{-1}{2} [/tex]
So the terminal point is [tex]( \frac{- \sqrt{3} }{2} , \frac{-1}{2} ) [/tex]
