Posted by **Tina P** on Tuesday, December 7, 2010 at 10:20am.

A ladder 10ft long rests against a vertical wall. If the bottom on the ladder slides away from the wall at 2 ft/s, how fast is the angle ladder makes with the ground changing when the bottom of the ladder is 5 ft from the wall.

- Calculus 1 -
**Reiny**, Tuesday, December 7, 2010 at 10:28am
Let the foot be x ft from the wall, let the angle formed by the ladder at the ground be Ø

given: dx/dt = 2 ft/s

find: dØ/dt when x = 5

x/10 = cosØ

x = 10cosØ

dx/dt = -10sinØ dØ/dt

when x=5,

height^2 + 5^2 = 10^2

height = √75

2 = -10(√75/10) dØ/dt

dØ/dt = - 2/√75 radians/second

= appr. - .23 rad/s

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