prove that 1+cosA +sinA/1+cosA-sinA= 1+sinA/cosA
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Answer:
Answer: The proof is done below.
Step-by-step explanation: We are given to prove the following trigonometric equality :
\dfrac{\sin\theta+1-\cos\theta}{\sin\theta-1+\cos\theta}=\dfrac{1+\sin\theta}{\cos\theta}.
sinθ−1+cosθ
sinθ+1−cosθ
=
cosθ
1+sinθ
.
We will be using the following formulas :
\begin{gathered}(i)~\dfrac{\sin\theta}{\cos\theta}=\tan\theta,\\\\\\(ii)~\sec\theta=\dfrac{1}{\cos\theta},\\\\\\(iii)~\sec^2\theta-\tan^2\theta=1\\\\(iii)~a^2-b^2=(a+b)(a-b).\end{gathered}
(i)
cosθ
sinθ
=tanθ,
(ii) secθ=
cosθ
1
,
(iii) sec
2
θ−tan
2
θ=1
(iii) a
2
−b
2
=(a+b)(a−b).
The proof is as follows :
\begin{gathered}\dfrac{\sin\theta+1-\cos\theta}{\sin\theta-1+\cos\theta}\\\\\\=\dfrac{\dfrac{\sin\theta+1-\cos\theta}{\cos\theta}}{\dfrac{\sin\theta-1+\cos\theta}{\cos\theta}}\\\\\\=\dfrac{\tan\theta+\sec\theta-1}{\tan\theta-\sec\theta+1}\\\\\\=\dfrac{\tan\theta+\sec\theta-(\sec^2\theta-\tan^2\theta)}{\tan\theta-\sec\theta+1}\\\\\\=\dfrac{\tan\theta+\sec\theta-(\sec\theta+\tan\theta)(\sec\theta-\tan\theta)}{\tan\theta-\sec\theta+1}\\\\\\=\dfrac{(\tan\theta+\sec\theta)(1-\sec\theta+\tan\theta)}{1-\sec\theta+\tan\theta}\\\\\\=\tan\theta+\sec\theta\\\\\\=\dfrac{sin\theta}{\cos\theta}+\dfrac{1}{\cos\theta}\\\\\\=\dfrac{1+\sin\theta}{\cos\theta}\\\\=R.H.S.\end{gathered}
sinθ−1+cosθ
sinθ+1−cosθ
=
cosθ
sinθ−1+cosθ
cosθ
sinθ+1−cosθ
=
tanθ−secθ+1
tanθ+secθ−1
=
tanθ−secθ+1
tanθ+secθ−(sec
2
θ−tan
2
θ)
=
tanθ−secθ+1
tanθ+secθ−(secθ+tanθ)(secθ−tanθ)
=
1−secθ+tanθ
(tanθ+secθ)(1−secθ+tanθ)
=tanθ+secθ
=
cosθ
sinθ
+
cosθ
1
=
cosθ
1+sinθ
=R.H.S.
Thus, we get
\dfrac{\sin\theta+1-\cos\theta}{\sin\theta-1+\cos\theta}=\dfrac{1+\sin\theta}{\cos\theta}.
sinθ−1+cosθ
sinθ+1−cosθ
=
cosθ
1+sinθ
.
Hence proved.
⁹
Answer: