Answer:
L = 5 m
Step-by-step explanation:
The ladder, the vertical wall and the ground form a right triangle. We call A and B the ends points of the ladder ( at the wall, and the ground)
If we call L the lenght of the leadder, we get
L² = y² + x²
Taking derivatives on both sides of the equation
0 = 2y Dy/dt + 2x Dx/dt
We know that Dy/dt = - 0,675 m/s (is sliding down , is decreasing)
And when x = 3 m Dx/dt = 0,9 m/s
So we can get y
0 = 2y*( -0,675) + 2*3*0,9
1,35y = 5,4
y = 5.4 /1,35 ⇒ y = 4
And L² = y² + x² ⇒ L = √ (4)² + (3)² ⇒ L √16 + 9
L = 5 m
