Name all the factors of (r+t)(e)

Other factors may appear when 'r', 't', and 'e' get certain values.
But the only factors you can count on, that don't depend on the
values of 'r', 't', and 'e' and always work,  are  (r + t)  and  'e' .

Sin(a)+cos(a)+cot(a)-1=2(csc(x)+1)