Why does cos θ become 0 for π/r radians?

[land_of_ice]

Why does cos θ, which normally equals x, become 0 when you evaluate this function for π/r radians?
(π/r means pi over r radians)
Why does cos θ, which normally equals x, become 0 when you evaluate this function for π/r radians?
It says that the point on the circle for this question is (0,1) so zero = x and y = 1 here.

 

[Mentallic]

For x=cos\theta, when x=0, \theta=\pi/2 (it can also be -\pi/2,3\pi/2 etc. but I don't think you need to deal with that right now).

When you're looking at the circle and any point on the circle (x,y) remember that cos\theta is adjacent/hypotenuse or x/1=x. So since the point on the circle is (0,1), the x value is 0 so cos(\pi/2)=0