Calculating Coefficient of Friction for a Crate on an Inclined Surface

[kaspis245]

Homework Statement

A 225 kg crate rests on a surface that is inclined above the horizontal at an angle of 20^o.
A horizontal force (F = 535 N parallel to the ground, not the incline) is required to start the crate moving down the incline. What is the coefficient of friction between the crate and the incline?

P.S. F_tr is a frictional force.

Homework Equations

Newton's laws of motion.

The Attempt at a Solution

It doesn't work.
The answer must be 0.665 .[/B]

 

[BvU]

Funny. That's exactly what I get. What is $\cos\alpha$ on your calculator ?

 

[kaspis245]

I missed one number xD. Sorry for wasting your time.