How can I optimize the area of a roof with a given wall length and angle?

[LHS]

Homework Statement

[PLAIN]http://img593.imageshack.us/img593/7536/unledci.png

Homework Equations

The Attempt at a Solution

I called the wall b, half the roof a, and the angle theta.
I get Area=2ab*sin(theta/2)+1/2 a^2 sin(theta)... try differentiating with respect to a and theta then setting them to zero.. doesn't do much

 

[eczeno]

the question asks you to minimize perimeter (minus the base), not area. the area is fixed and so can be used to reduce the number of variables.

 

[LHS]

Oh I meant differentiate b with respect to a and theta. But yes, you are correct, silly me!