y=cos64θ-sin64怎么化简?（64是次数）

cos^64θ-sin^64θ
=(cos^32θ-sin^32θ)(cos^32θ+sin^32θ)
=(cos^16θ-sin^16θ)(cos^16θ+sin^16θ)(cos^32θ+sin^32θ)
=(cos^8θ-sin^8θ)(cos^8θ+sin^8θ)(cos^16θ+sin^16θ)(cos^32θ+sin^32θ)
=(cos^4θ-sin^4θ)(cos^4θ+sin^4θ)(cos^8θ+sin^8θ)(cos^16θ+sin^16θ)(cos^32θ+sin^32θ)
=(cos^2θ-sin^2θ)(cos^2θ+sin^2θ)(cos^4θ+sin^4θ)(cos^8θ+sin^8θ)(cos^16θ+sin^16θ)(cos^32θ+sin^32θ)
=cos(2θ)(cos^4θ+sin^4θ)(cos^8θ+sin^8θ)(cos^16θ+sin^16θ)(cos^32θ+sin^32θ)