9514 1404 393
Answer:
1.9 degrees per second
Step-by-step explanation:
The angle α the line makes with the water can be described by ...
Sin = Opposite/Hypotenuse
sin(α) = 10/(25 -1.9t)
Taking derivatives gives ...
α'·cos(α) = -10(-1.9)/(25 -1.9t)²
Then the rate of change of the angle at t=0 is ...
α' = 19/(25²·cos(α))
Of course, cos(α) = √(1 -sin(α)²) = √(1 -(10/25)²) = √(21/25), so we have ...
α' = 19/(125√21) . . . radians/second
α' ≈ 0.033269 radians/s ≈ 1.90 degrees/s
