You may want to start using the \frac command in LaTeX to input fractions properly. For example \frac{a}{b} would give you this: . I say this because I have a feeling there will be some confusion as to what you wrote. For example, #2, is it this:

or this?

#4 and #5 presents the same problems on interpretation.

#3 looks straightforward, so I'll do that.

Divide both sides by 2 pi:

Square both sides:

Cross-multiply:

And divide both sides by T^2: