sketch this curve given in terms of the parameter alpha
x = cos alpha, y = sin alpha
i got x= 0 for y = 1, -1 and y = 0 for x = 1,-1 but from here i dont know how to sketch the graph! any suggestions?
Obviously you are using degrees as argument of the trigonometric functions. So choose those values of $\displaystyle \alpha$ where you know the trig values:
$\displaystyle \alpha = 60^\circ \rightarrow x = \frac12, y = \pm \frac12 \sqrt{3}$
$\displaystyle \alpha = 30^\circ \rightarrow x = \frac12 \sqrt{3}, y = \pm \frac12 $
and so on ...