(Solved): A ladder a=13m long is leaning against a wall. If the lower end of the ladder slides away from t ...

A ladder $$a=13\mathrm{m}$$ long is leaning against a wall. If the lower end of the ladder slides away from the wall at the rate of $$b=0.5\mathrm{m}/\mathrm{s}$$, at what rate is the inclination $$?$$ of the ladder with respect to the ground changing when the lower end is $$4\mathrm{m}$$ from the wall? (Use symbolic notation and fractions where needed.) $$\frac{d?}{dt}$$ radians/s