Question

prove that:
sec^4A-cos^4A =1-2cos^2A

Answer 1

Oops , your question is wrong ! Plz write correct question .

Correct question is ---> sin⁴A - cos⁴A = 1 - 2cos²A

LHS = sin⁴A - cos⁴A

= (sin²A - cos²A)(sin²A + cos²A)

As you know, sin²x + cos²x = 1

So, sin²A + cos²A = 1

∴ LHS = (sin²A - cos²A) × 1

= (1 - cos²A - cos²A) [ sin²x = 1 - cos²x from identities ]

= 1 - 2cos²A = RHS

[Hence, proved]

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Answer 2

Step-by-step explanation:

hope this helps you the square brackets are the formulas from which you get the eqn.

hope u'll understand