Question

cos power 4 - sin power 4 = 1 - 2 sin square . prove that

Answer 1

Answer :

Now,

cos⁴A - sin⁴A

= (cos²A)² - (sin²A)²

= (cos²A + sin²A) (cos²A - sin²A)

= 1 (1 - sin²A - sin²A),

since sin²A + cos²A = 1

= 1 - 2 sin²A

Hence, proved.

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