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\(sec^{2}x + cosec^{2}x - sec^{2}xcosec^{2}x =\)

  • A.\(sec^{2}x\)
  • B.\(cosec^{2}x\)
  • C.\(cot^{2}x\)
  • D.1
  • E.0

Answer: E

The value is 0.

Add the first two terms over a common denominator.

\[ \begin{aligned} sec^{2}x + cosec^{2}x &= \frac{1}{\cos^{2}x} + \frac{1}{\sin^{2}x} \\ &= \frac{\sin^{2}x + \cos^{2}x}{\sin^{2}x\cos^{2}x} = sec^{2}x\,cosec^{2}x \end{aligned} \]

So the sum of the squares equals their product and the expression is 0 for every x where it is defined. The answers 1 or a single trigonometric function come from stopping before using \(\sin^{2}x + \cos^{2}x = 1\).

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