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CBSE Class 10 Math 2023 All Sets Solved Paper

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Question : 18 of 20
Marks: +1, -0
(cos⁡4A−sin⁡4A)(\cos^4 A - \sin^4 A) on simplification, gives
Solution:  
cos⁡4A−sin⁡4A\cos^4 A - \sin^4 A
=(cos⁡2A−sin⁡2A)(cos⁡2A+sin⁡2A)=(\cos^2 A - \sin^2 A)(\cos^2 A+\sin^2 A)
=(cos⁡2A−sin⁡2A)⋅1=(\cos^2 A - \sin^2 A)\cdot 1
=cos⁡2A−(1−cos⁡2A)=\cos^2 A -(1-\cos^2 A)
=2cos⁡2A−1=2\cos^2 A -1
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