Dear aspirant,
I would like to recommend you to kindly review your question from wherever you sent. Because I don't think this type of question will be asked . I think you are asked to find f'(x) and not f(x) . But still if it is required to find then the answer will be 1-1/√2.
Question : If $\sec x- \cos x$ = 4, then what will be the value of $\frac{\left(1+\cos ^2x\right)}{\cos x}?$
Option 1: $\frac{9}{4}$
Option 2: $\frac{1}{4}$
Option 3: $2\sqrt{5}$
Option 4: $\sqrt{5}$
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