since you have a triangle- formed by the ground and the height and the string, you can use trig.
in trig the Sin = opposite over hypotenuse
since your angel is 58, and it is the angle of the string off the ground, then sin58=opp/hypotenuse
sin58=x/45
^^^ here, x is the height (what youre looking for), and 45 is the string lenght
multiple the whole thing by 45 to get
45sin58=x
then on your calculator do
sin(58)
then take that answer
and multiply by 45
this answer is the height of the kite in yards!