Rate of Change of theta in ladder to wall.

[ryandamartini]

Homework Statement

A ladder 10 ft long rests against a vertical wall. If the bottom of the ladder slides away from the wall at a rate of 1.3 ft/s, how fast is the angle between the ladder and the ground changing when the bottom of the ladder is 6 ft from the wall? Evaluate your answer numerically.

Homework Equations

a^2+b^2=c^2 ?
Theta(dot) is change of time respect to theta.

The Attempt at a Solution

In class he went over finding the rate of theta, getting the equation Theta(dot)=X/(10cos(45) I tried plugging in 6 for X, I just really don't know what to do here.

 

[HallsofIvy]

I would suggest that instead of using a²+ b²= c², which does not involve an angle, you use a= bcos(\theta) where a is the "hypotenuse" (the length of the ladder) and a is the "near side" (the distance from the foot of the ladder to the wall).

 

[Rayquesto]

theta=tan(y/x) right
then what the formula to find the change in theta at any given point?