Trig problem need help?

r=sqrt(x^2+y^2) or sqrt(36+64) or 10. Now since both x and y are positive, we are in quadrant 1 and all trig values are positive. Since sin u=y/r and cos u=x/r. we can find the values of all trig functions from this. In this case csc u=1/sin u. Now since sin u=8/10 or 4/5 we find that csc u=5/4.