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Simplify cos x1−sin x\frac{\text{cos}\space x}{1-\text{sin}\space x}1−sin xcos x​​ using trigonometric identities:
Question

Simplify cos x1sin x\frac{\text{cos}\space x}{1-\text{sin}\space x}​ using trigonometric identities:

A.

sec xx​ + tan xx​​

B.

sec xx​ - tan xx​​

C.

1sin xcos x\frac{1-\text{sin}\space x}{\text{cos}\space x}​​

D.

1cos xsin x\frac{1-\text{cos}\space x}{\text{sin}\space x}​​

Correct option is A

Multiply both the numerator and the denominator by the conjugate of the denominator, which is 1+sinx:cosx1sinx1+sinx1+sinx=cosx(1+sinx)(1sinx)(1+sinx)Simplify the DenominatorThe denominator is a difference of squares:(1sinx)(1+sinx)=1sin2xUsing the Pythagorean identity 1sin2x=cos2x:cosx(1+sinx)cos2xCancel cosx in the Numerator and Denominator1+sinxcosxThis can be written as:1cosx+sinxcosx=secx+tanx\begin{aligned}&\text{Multiply both the numerator and the denominator by the conjugate of the denominator, which is } 1 + \sin x: \\&\qquad \frac{\cos x}{1 - \sin x} \cdot \frac{1 + \sin x}{1 + \sin x} = \frac{\cos x (1 + \sin x)}{(1 - \sin x)(1 + \sin x)} \\\\&\textbf{Simplify the Denominator} \\\\&\text{The denominator is a difference of squares:} \\&\qquad (1 - \sin x)(1 + \sin x) = 1 - \sin^2 x \\\\&\text{Using the Pythagorean identity } 1 - \sin^2 x = \cos^2 x: \\&\qquad \frac{\cos x (1 + \sin x)}{\cos^2 x} \\\\&\textbf{Cancel } \cos x \text{ in the Numerator and Denominator} \\&\qquad \frac{1 + \sin x}{\cos x} \\\\&\text{This can be written as:} \\&\qquad \frac{1}{\cos x} + \frac{\sin x}{\cos x} = \sec x + \tan x\end{aligned}​​

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