1)
\(EI=\frac{d^2v}{dx^2}+\frac{P}{EI}v=0\) 
\(EI=\frac{d^2v}{dx^2}=M\)
\(M=-Pv\)
\(EI=\frac{d^2v}{dx^2}-Pv\)
\(v=0\ en\ X\ \ y\ C2=0\)
\(SIN\left(\sqrt{\frac{P}{EI}}L\right)=0\)
\(\sqrt{\frac{P}{EI}}L=n\pi\)
\(\left(\sqrt{\left(\frac{P}{EI}\right)^2}L^{2\ }=\left(n\pi\right)^2\right)\)
\(L^2=n\pi^2\)