Answer:
10.2 ft
Step-by-step explanation:
The swimming pool would make a right triangle with the pool, if the bottom of the slide touched the bottom of the pool. Â
If we take the right triangle that would be formed, we have the 50° angle of elevation and the hypotenuse of the triangle, 12.
We are trying to find the height of the platform; this would be the side opposite the 50° angle.  The ratio of opposite/hypotenuse is sine; this gives us the equation
sin 50 = x/12
Multiply both sides by 12:
12sin 50 = (x/12)(12)
12sin 50 = x
9.2 = x
Since the bottom of the slide is 1 foot above the ground, the height of the platform is 9.2+1 = 10.2.