If theta is "the angle between the ladder and the wall of the house" and x is the distance from the wall to the foot of the house, then, yes it is.
What equation did you get and what "wrong answer" did you get?I took the implicit derivative of both sides but ended up with a
sec^2 (theta) function that led to the wrong answer.
The book does not explain how to find angles in terms of related rates. How is this done? I will then use your steps to solve similar questions. Thank you.