.
simplify
tan^2x+secx-1/secx-1
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Be aware: the "solution" of @josgarithmetic is TOTALLY INADEQUATE,
since he simplifies the formula DIFFERENT from the given in the condition.
Next. Please read the following VERY ATTENTIVELY.
Your formula is ambigous.
It can be read as
(tan^2x+secx-1)/(secx-1), or as
tan^2x + (secx-1)/(secx-1), or as
tan^2x + secx - (1/secx-1), or as
tan^2x + secx - (1/secx) - 1
and, probably, by many other ways.
To avoid ambiguity, use PARENTHESES to clearly and explicitly show which part of your formula
is the numerator and which part is denominator.
When you post the formula correctly presented, we, the tutors of this forum, will provide the correct solution.