How Do Forces Affect the Deformation and Young's Modulus of a Book?

[Schoomy]

Homework Statement

A large book has forces of magnitude 14 N applied in opposite directions to two opposite faces of area 42 cm². The thickness of the book (L) is 2.0 cm. The deformation angle (g) is 8.4°.

1) what is change in X?
2) What is young's modulus for the book?

http://dl.getdropbox.com/u/119186/Picture%201.png

Homework Equations

I tried getting change in x doing 2cos(8.4) but I'm horrible at trig. What should I have done?

Once I do that, I can just plug it all into F/A = S*deltaX/L
Right?

What should I be doing to get the change in X?

 

[Schoomy]

And I should have just used SIN!

Can someone explain to me why I needed to use SIN over COS in this example? I just don't get it.

What does SIN or COS intrinsically mean, represent, etc?