Math, asked by shakjaw, 3 months ago

1+cos a + sin a / 1+cos a - sin a = 1+sin a/ cos a​

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Answered by durgarani18
0

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Answered by Intelligentcat
8

Given :

:\implies\bf{\dfrac{1 + cos A + sin A}{1+cos A - sin A} = \dfrac{1 + sin A}{cos A}}\\ \\ \\

Proof :

Taking L. H. S

:\implies\bf{\dfrac{1 + cos A + sin A}{1+cos A - sin A}}\\ \\ \\

Dividing Numerator and Denominator by Cos A

:\implies\sf{\dfrac{1}{Cos A} + \dfrac {\cancel Cos A} {\cancel Cos A} + \dfrac{Sin A}{Cos A} \div \dfrac{1}{cos A} + \dfrac {\cancel Cos A} {\cancel Cos A} - \dfrac{sin A}{cos A}}\\ \\ \\

Identity Used :

  • \implies\bf{ \dfrac{1}{Cos A} = Sec A}\\ \\ \\
  • \implies\bf{ \dfrac{Sin A}{Cos A} = Tan A}\\ \\ \\

:\implies\sf {\dfrac{Sec A + 1 + tan A}{Sec A + 1 - tan A}}\\ \\ \\

Rationalising with Denominator

That means multiply the Denominator after changing its sign.

:\implies\sf{\dfrac{Sec A + 1 + tan A}{(Sec A + 1) - tan A} \times \dfrac{Sec A + 1 + tan A}{Sec A + 1 + tan A}}\\ \\ \\

Identity Used :

  • \implies\bf{Sec^{2} A - Tan^{2} A =1}\\ \\ \\
  • \implies\bf{1+ Tan^{2} A = Sec^{2}A}\\ \\ \\

:\implies\sf {\dfrac{(Sec A + 1 + tan A)^{2}} {(Sec A + 1)^{2} - tan^{2} A}}\\ \\ \\

Identity Used :

  • \implies\sf{(a + b + c) ^{2} = a^{2} + b^{2} + c^{2} + 2ab + 2bc + 2ca}\\ \\ \\

:\implies\sf {\dfrac{Sec^{2} A + 1 + tan^{2} A + 2Sec A + 2Tan A + 2Sec A Tan A}{1 + Sec^{2} A + 2Sec A - Tan^{2} A}}\\ \\ \\

:\implies\sf {\dfrac{Sec^{2} A + Sec^{2}A + 2Sec A + 2Tan A + 2Sec A Tan A}{2 + 2Sec A}}\\ \\ \\

:\implies\sf {\dfrac{2Sec^{2} A + 2SecA + 2Tan A + 2Sec A Tan}{2 + 2Sec A}}\\ \\ \\

Taking 2 common -

:\implies\sf {\dfrac{\cancel 2[sec A (Sec A + 1) + Tan A(1 + Sec A) ]}{\cancel 2(1 + Sec A)}}\\ \\ \\

:\implies\sf {\dfrac{(Sec A + Tan A)  (Sec A + 1)} {(1 + Sec A)}}\\ \\ \\

:\implies\sf {Sec A + Tan A}\\ \\ \\

:\implies\sf {\dfrac{1}{cos A} + \dfrac{Sin A}{Cos A}}\\ \\ \\

Identity Used :

  • \implies\bf{Sec A = \dfrac{1}{Cos A}}\\ \\ \\
  • \implies\bf{ Tan A = \dfrac{SinA}{Cos A}}\\ \\

Taking L. C. M

:\implies\bf {\dfrac{1 + Sin A}{Cos A}}\\ \\ \\

Hence,

\boxed{\therefore{\sf {\dfrac{1 + Sin A}{Cos A} = RHS}}}\\ \\ \\

Proved!!

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