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(2cos^2A-1)^2÷cos^4A-sin^4=1-2sin^2A
[tex](2 \cos(2) a - 1) {}^{2} \div \cos(4) - \sin(4) = 1 - 2 \sin(2) a[/tex]


Sagot :

Answer:

Correct Question :-

[tex]\longmapsto \: \sf\dfrac{{(2cos^2A - 1)}^{2}}{cos^4A - sin^4A} =\: 1 - 2sin^2A[/tex]

Solution :-

Taking LHS :

[tex]\dashrightarrow \sf \dfrac{{(2cos^2A - 1)}^{2}}{cos^4A - sin^4A}[/tex]

[tex]\implies \sf \dfrac{{(2cos^2A - 1)}^{2}}{{(cos^2A)}^{2} - {(sin^2A)}^{2}}[/tex]

[tex]\implies \sf \dfrac{{(2cos^2A - 1)}^{2}}{(cos^2A + sin^2A)(cos^2A - sin^2A)} \: \bigg\lgroup a^2 - b^2 =\: (a + b)(a - b)\bigg \rgroup\\[/tex]

[tex]\implies \sf \dfrac{{(2cos^2A - 1)}^{2}}{(cos^2A - sin^2A)}[/tex]

[tex]\implies \sf \dfrac{\{2(1 - sin^2A)- 1\}^2}{1 - sin^2A - sin^2A} \: \bigg\lgroup cos^2A =\: 1 - sin^2A\bigg \rgroup\\[/tex]

[tex]\implies \sf \dfrac{(2 - 2sin^2A - 1)^2}{1 - 2sin^2A}[/tex]

[tex]\implies \sf \dfrac{(2 - 1 - 2sin^2A)^2}{1 - 2sin^2A}[/tex]

[tex]\implies \sf \dfrac{(1 - 2sin^2A)^2}{1 - 2sin^2A}[/tex]

[tex]\implies \sf \dfrac{\cancel{(1 - 2sin^2A)}(1 - 2sin^2A)}{\cancel{1 - 2sin^2A}}[/tex]

[tex]\implies \sf\bold{\red{1 - 2sin^2A}} \: \: \bigg\lgroup \bold{LHS}\bigg \rgroup[/tex]

Again, taking RHS :

[tex]\dashrightarrow \sf 1 - 2sin^2A[/tex]

[tex]\implies\sf\bold{\red{1 - 2sin^2A}} \: \: \bigg\lgroup \bold{RHS}\bigg \rgroup[/tex]

[tex]{\large{\pink{\bold{\underline{\leadsto\: LHS =\: RHS}}}}}[/tex]

[tex]\clubsuit \: \sf\boxed{\bold{\green{Hence, Proved}}}[/tex]

[tex]\rule{150}{2}[/tex]

Extra Formula Related to Trigonometry :

[tex]\diamondsuit\: \sf\bold{\purple{Trigonometry\: Identities\: :-}}[/tex]

[tex]\sf cos^2\theta + sin^2\theta =\: 1[/tex]

[tex]\sf 1 + tan^2\theta =\: sec^2\theta[/tex]

[tex]\sf 1 + cot^2\theta =\: cosec^2\theta[/tex]

[tex]\diamondsuit \: \sf\bold{\purple{Trigonometry \: Complementary\: Angle\: Identities\: :-}}[/tex]

[tex]\sf sin(90 - \theta) =\: cos\theta[/tex]

[tex]\sf cos(90 - \theta) =\: sin\theta[/tex]

[tex]\sf tan(90 - \theta) =\: cot\theta[/tex]

[tex]\sf cot(90 - \theta) =\: tan\theta[/tex]

[tex]\sf sec(90 - \theta) =\: cosec\theta[/tex]

[tex]\sf cosec(90 - \theta) =\: sec\theta[/tex]