Answer:
I am pretty sure it is the 3rd one
(In geometry, an isosceles triangle is a triangle that has two sides of equal length. And i think 3 of them are an isosceles triangle)
Step-by-step explanation:
Given that,
The length of a ladder, H = 20 feet
The height of the wall, h = 15 ft
We know that,

h is perpendicular and H is hypotenuse
So,

Now using Pythagoras theoerm,

Hence, the angle made by the ladder and the ground is 48.59° and the ladder is 13.2 feet from the wall on the ground.