You can picture this as a right angle triangle, with the string being the hypotenuse.
You are given the height of the triangle (36 feet), which is also the length of the perpendicular side that is opposite the 58 degree angle. Since you have the opposite side and want to find the hypotenuse's length, you have to use the trigonometric ratio of sin
sin 58 = opposite/hypotenuse
sin 58 = 36/hypotenuse
Hypotenuse = 36/sin 58
Just punch those numbers into your calculator and you should get an answer of around 42.5 feet
Hope I helped!! xx