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I'm having kind of a trouble trying to understand how to solve this following simple problem.If somebody is willing to help me i'll be very greatfull!

I'll try to translate it from portuguese and hope everything written is correct.

## Homework Statement

A ladder 10 metters in length and whose gravity center lies in its center is supported on the ground( with friction ) and a wall (without friction).The weight of the ladder is 400 N and a person's weight is 600 N, sin(theta)=0,80 and cos (theta)=0,60,Calculate:

a)The intensity of the force applied on the ladder by the wall.

Obs.:The person climbed the ladder 8 metters.

## Homework Equations

## The Attempt at a Solution

What i found out of nothing was this:

M1 + M2 + M3 = 0

4,8(600) + 3(400) = 8F

F = 510N

But i could not understand it.Can somebody please show me how is this fitted?And why?

Thanks in advanced!

I hope it is not too confusing.