How would you prove:

(1-tan theta) squared= sec squared theta -2 tan theta

This isn't a bad one by comparison.

Exapnd out and look at it.



Now, what does equal?

(1-tan theta) squared = sec squared theta - 2 tan theta
1 + tan square theta - 2 tan theta
sec square theta - 2 tan theta
[since 1+tan square theta = sec square theta]

cot theta + (sin theta/1+cos theta)= csc theta

Could you avoid double posting please?

I already answered your question here