this interval indicate to which quarter

This is just a Pythagorean right triangle in the 4th quad where x = 5, y = -12, and the hypoteneuse (r) = 13.

And the cosine is given by....

x/r  = 5/13  = Answer (c)

sorry .. but how do you know that it is in the 4th quad ! 

and why you put y=-12 !! 

It's in the 4th quadrant because the angle "x" lies between -pi/2  and 0.....

And remember that in the 4th quadrant, x is positive and y is negative. And the tanx = y/x = -12/5

Does that make sense, xvxvxv ???

I think that I forgot this information 

if I not mistaken I think that there is a circle that illustrate this information ! 

do you know it .. ! because it will help me understand 

Here's a pretty good page that will help you with this.....

http://www.themathpage.com/aTrig/unit-circle.htm

thanx my friend 

Remember 

All Stations To Central

All are positive in the first quad

sin is pos in the second

tan is pos in the third and

cos is pos in the 4th.     

We used to say "All Students Take Calculus"...but I like "All Stations To Central," too!!  (It sounds like something right out of the old TV program..."Car 54, Where Are You??" )