(1-sin^6α-cos^6α)/(sin²α-sin^4α)={1-[(sin²α+cos²α)(sin^4α-sin²αcos²α+cos^4α)]}/sin²α(1-sin²α)
=[1-（sin^4α-sin²αcos²α+cos^4α)]/sin²αcos²α=[1-(sin^4α+2sin²αcos²α+cos^4α-3sin²αcos²α)/sin²αcos²α={1-[(sin²α +cos²α)²-3sin²αcos²α]}/sin²αcos²α=3.