Added a new image of an LRC circuit
Updated the first lecture introducting seoncd order DEs
Merge pull request #53 from KellyBlack/black_dev

Updates to the first lecture on second order DEs.
Updated the lecture on finding solutions for constant coeff. des with real valued roots.
Merge pull request #54 from KellyBlack/black_dev

Updated the lecture on finding solutions for constant coeff. des with re...
one typo on Wednesday note, and some minor changes on friday note
Added new images and a matlab file to generate them for the discussion on complex roots for constant coefficient equations.
Updated the discussion on complex roots to linear, constant coeff. equations.
fix the conflicts
Merge pull request #34 from guangmingyao/yao_dev

Yao dev