Recent content by NewNuNeutrino

Hello, I was working through some quantum homework and was looking for some help online and ran across this: http://physics.uwyo.edu/~yurid/QM/Handout5.pdf I was wondering if anyone knew what textbook this is from? I tried searching excerpts from the book, but alas, no results. Thanks!

I know where he gets d_{12}=\sqrt{(-a+x_{3}-x_{2})^{2}+(a+y_{3}-y_{2})^{2}} but I don't know what approximation he uses to get to d_{12}=\sqrt{2}a-\frac{1}{\sqrt{2}}(x_{3}-x_{2})+\frac{1}{\sqrt{2}}(y_{3}-y_{2}) It seems like it should be simple, but I can't figure it out. Thank you!

Homework Statement A molecule consists of three identical atoms located at the vertices of a 45 degree right triangle. Each pair of atoms interacts by an effective spring potential, with all spring constants equal to k. Consider only planar motion of this molecule. What are 6 normal modes and...