How do you prove cos4(x) - sin4(x) = cos (2x)?

1.	How do you prove cos4(x) - sin4(x) = cos (2x)?
Answer» Hence proved thatcos⁴(x) - sin⁴(x) = cos (2x) sin(θ) is the ratio of the opposite (base) side to the hypotenuse, while cos(θ) is the ratio of the adjacent (perpendicular) side to the hypotenuse.

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