Repeat the above steps and click Ink New Equation in the drop-down list of Equation button. I tried the copy and paste it comes as picture and the baseline doesnt mach the text. There is also an entire paper PDF about using plaintext to type up formulas.
When you insert a new equation control Insert Equation Insert New Equation youll see a control box with just Type equation here.
For the complicated equations use a library to help Check out MathJax. You can select portions of the equation and edit them as you go and use the preview box to make sure Word is correctly interpreting your handwriting. Youll see this on the far right in the Symbols group. Find the insert button hit it then to the right In Word 2010 is a place for equation symbols additionally you can use the Character editor there is Cambria Math which has most.