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The expression \(\frac{\sin A}{1-\cot A} + \frac{\cos A}{1-\tan A}\) can be simplified to:

  • A.0
  • B.1
  • C.\(\sin a + \cos a\)
  • D.\(\sin a - \cos a\)

Answer: C

Convert to sin and cos: \(\frac{\sin A}{1-\frac{\cos A}{\sin A}} + \frac{\cos A}{1-\frac{\sin A}{\cos A}} = \frac{\sin^2 A}{\sin A - \cos A} + \frac{\cos^2 A}{\cos A - \sin A}\)

= \(\frac{\sin^2 A}{\sin A - \cos A} - \frac{\cos^2 A}{\sin A - \cos A}\)

= \(\frac{\sin^2 A - \cos^2 A}{\sin A - \cos A}\)

= \(\frac{(\sin A - \cos A)(\sin A + \cos A)}{\sin A - \cos A} = \sin A + \cos A\).

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