Rotational Equilibrium (1 Viewer)

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1. The problem statement, all variables and given/known data
A house painter stands 3.0 m above the ground on a 5.0 m long ladder that leans against the wall at a point 4.7 m above the ground. The painter weighs 680 N and the ladder weights 120 N. Assuming no friction between the house and the upper end of the ladder, find the force of friction that the driveway exerts on the bottom of the ladder.


2. Relevant equations
net Torque=zero
Net force=zero


3. The attempt at a solution
(680 x 3.0 x cos 70) + (120 x 2.5 x cos 70)/ (5.0 x cos 20)
=170 N

My books says 180 N is the answer, what am i doing wrong????? So frustrated!
 

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