Question

cos⁴theta-sin⁴theta =2cos²theeta-1 ​

Answer 1

Answer:

=> cos^4 theeta - sin^4theeta

• sin^4theeta can be written as

( sin^2theeta)^2

=> (sin^2theeta)^2 = (1 - cos^2theeta)^2

=> cos^4 theeta - (1 - cos^2theeta)^2

• ( 1 - cos^2theeta)^2 = ( 1 + cos^4 theeta -

2cos^2theeta

=> cos^4 theeta- ( 1 + cos^4 theeta - 2cos^2theeta)

=>2cos^2theeta - 1

Hence Proved.

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