Tính đạo hàm của hàm số sau: \(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamyEaiabg2 % da9maalaaabaGaaGymaaqaaiGacogacaGGVbGaai4CamaaCaaaleqa % baGaaGOmaaaakiaadIhacqGHsislciGGZbGaaiyAaiaac6gadaahaa % WcbeqaaiaaikdaaaGccaWG4baaaiabg2da9maalaaabaGaaGymaaqa % aiGacogacaGGVbGaai4CaiaaikdacaWG4baaaaaa!4998! y = \frac{1}{{{{\cos }^2}x - {{\sin }^2}x}} = \frac{1}{{\cos 2x}}\)
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Lời giải:
Báo sai\(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamyEaiaacE % cacqGH9aqpdaWcaaqaaiabgkHiTmaabmaabaGaci4yaiaac+gacaGG % ZbGaaGOmaiaadIhaaiaawIcacaGLPaaadaahaaWcbeqaaiaac+caaa % aakeaadaqadaqaaiGacogacaGGVbGaai4CaiaaikdacaWG4baacaGL % OaGaayzkaaWaaWbaaSqabeaacaaIYaaaaaaakiabg2da9maalaaaba % Gaci4CaiaacMgacaGGUbGaaGOmaiaadIhacaGGUaWaaeWaaeaacaaI % YaGaamiEaaGaayjkaiaawMcaamaaCaaaleqabaGaai4laaaaaOqaai % GacogacaGGVbGaai4CamaaCaaaleqabaGaaGOmaaaakiaaikdacaWG % 4baaaiabg2da9maalaaabaGaaGOmaiGacohacaGGPbGaaiOBaiaaik % dacaWG4baabaGaci4yaiaac+gacaGGZbWaaWbaaSqabeaacaaIYaaa % aOGaaGOmaiaadIhaaaGaaiOlaaaa!643F! y' = \frac{{ - {{\left( {\cos 2x} \right)}^/}}}{{{{\left( {\cos 2x} \right)}^2}}} = \frac{{\sin 2x.{{\left( {2x} \right)}^/}}}{{{{\cos }^2}2x}} = \frac{{2\sin 2x}}{{{{\cos }^2}2x}}.\)