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EEJ MAIN Mathematics
QUESTION #7462
Question 1
The expression \(\frac{\tan A}{1-\cot A} + \frac{\cot A}{1-\tan A}\) can be written as:
Correct Answer Explanation
Rewriting in terms of sine and cosine: \(\frac{\frac{\sin A}{\cos A}}{1-\frac{\cos A}{\sin A}} + \frac{\frac{\cos A}{\sin A}}{1-\frac{\sin A}{\cos A}} = \frac{\frac{\sin A}{\cos A}}{\frac{\sin A - \cos A}{\sin A}} + \frac{\frac{\cos A}{\sin A}}{\frac{\cos A - \sin A}{\cos A}} = \frac{\sin^2 A}{\cos A(\sin A - \cos A)} + \frac{\cos^2 A}{\sin A(\cos A - \sin A)}\). Taking common denominator: \(= \frac{\sin^2 A}{\cos A(\sin A - \cos A)} - \frac{\cos^2 A}{\sin A(\sin A - \cos A)} = \frac{\sin^3 A - \cos^3 A}{\sin A \cos A (\sin A - \cos A)}\). Using \(a^3-b^3 = (a-b)(a^2+ab+b^2)\): \(= \frac{(\sin A - \cos A)(\sin^2 A + \sin A \cos A + \cos^2 A)}{\sin A \cos A (\sin A - \cos A)} = \frac{1 + \sin A \cos A}{\sin A \cos A} = \frac{1}{\sin A \cos A} + 1 = \sec A \csc A + 1\).
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