Answer:
Let F1x = force of wall on ladder
F1x = F2x   the force of friction  (balances horizontal forces)
F2y = W Â Â Â balance weight of ladder
F2x = μ F2y    force of friction on ladder
F1x L sin θ = W L / 2 cos θ   balance torque about point F2
tan θ  = W / (2 F1x)   previous equation
Now   μ W = μ F2y = F2x = F1x  from above
So tan θ  = W / (2 μ W) = 1 / (2 μ ) = 1 / .64
tan θ = 1.56
θ = 57.4 deg