Deriving an equation through a free body diagram

[xgdoyo]

Homework Statement

Use a Free body diagram to show that :Tanθ=static friction, on an incline plane

Homework Equations

FF/FN= coeficiant of friction

The Attempt at a Solution

I know I must get an angle to have a tan of the Force of friction and a Normal force, but I don't understant why i need the the angle

 

[BruceW]

You should draw out the free body diagram (since that's what the question asks) and that's usually the best way to go about solving these kinds of questions anyway.

What was the actual question? It would make more sense if it asked you to show that:
$$tan(\theta) \leq \mu_s$$
(where $\mu_s$ is the coefficient of static friction). And remember that the friction force can be less than its maximum possible value, which is why there is an inequality sign.