Based on my understanding, 20 feet serves as the hypotenuse of the triangle created when the bleacher rises from the ground at an angle of 33°.
sin θ = opposite / hypotenuse
cos θ = adjacent / hypotenuse
tan θ = opposite / adjacent
sin 33° = opposite / 20 ft
sin 33° x 20ft = opposite
0.544 x 20 = opposite
10.89 ft = opposite
cos 33° = adjacent / hypotenuse
cos 33° x 20 ft = adjacent
0.839 x 20 = adjacent
16.77 ft = adjacent
I think the the length of the bleachers along the ground is the value of the adjacent which is 16.77 ft.
