Biết \(% MathType!MTEF!2!1!+- % feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaa8qCaeaada % qadaqaaiaaigdacqGHRaWkcaWG4baacaGLOaGaayzkaaGaci4yaiaa % c+gacaGGZbGaaGOmaiaadIhacaqGKbGaamiEaaWcbaGaaGimaaqaam % aalaaabaGaeqiWdahabaGaaGinaaaaa0Gaey4kIipakiabg2da9maa % laaabaGaaGymaaqaaiaadggaaaGaey4kaSYaaSaaaeaacqaHapaCae % aacaWGIbaaaaaa!4C8B! \int\limits_0^{\frac{\pi }{4}} {\left( {1 + x} \right)\cos 2x{\rm{d}}x} = \frac{1}{a} + \frac{\pi }{b}\) \((a, b \in Z^*)\). Giá trị của tích a.b bằng
Suy nghĩ và trả lời câu hỏi trước khi xem đáp án
Lời giải:
Báo sai\(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVCI8FfYJH8YrFfeuY-Hhbbf9v8qqaqFr0xc9pk0xbb % a9q8WqFfeaY-biLkVcLq-JHqpepeea0-as0Fb9pgeaYRXxe9vr0-vr % 0-vqpWqaaeaabiGaciaacaqabeaadaqaaqaaaOqaamaaceaaeaqabe % aacaWG1bGaeyypa0JaaGymaiabgUcaRiaadIhaaeaacaqGKbGaamOD % aiabg2da9iaadogacaqGVbGaae4CaiaaikdacaWG4baaaiaawUhaai % abgkDiEpaaceaaeaqabeaacaqGKbGaamyDaiabg2da9iaabsgacaWG % 4baabaGaamODaiabg2da9maalaaabaGaaGymaaqaaiaaikdaaaGaci % 4CaiaacMgacaGGUbGaaGOmaiaadIhaaaGaay5Eaaaaaa!5377! \left\{ \begin{array}{l} u = 1 + x\\ {\rm{d}}v = c{\rm{os}}2x \end{array} \right. \Rightarrow \left\{ \begin{array}{l} {\rm{d}}u = {\rm{d}}x\\ v = \frac{1}{2}\sin 2x \end{array} \right.\)
\(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVCI8FfYJH8YrFfeuY-Hhbbf9v8qqaqFr0xc9pk0xbb % a9q8WqFfeaY-biLkVcLq-JHqpepeea0-as0Fb9pgeaYRXxe9vr0-vr % 0-vqpWqaaeaabiGaciaacaqabeaadaqaaqaaaOabaeqabaGaamysai % abg2da9maalaaabaGaaGymaaqaaiaaikdaaaWaaeWaaeaacaaIXaGa % ey4kaSIaamiEaaGaayjkaiaawMcaaiGacohacaGGPbGaaiOBaiaaik % dacaWG4bWaaqqaaqaabeqaamaalaaabaGaeqiWdahabaGaaGinaaaa % aeaacaaIWaaaaiaawEa7aiabgkHiTmaalaaabaGaaGymaaqaaiaaik % daaaWaa8qCaeaaciGGZbGaaiyAaiaac6gacaaIYaGaamiEaiaabsga % caWG4baaleaacaaIWaaabaWaaSaaaeaacqaHapaCaeaacaaI0aaaaa % qdcqGHRiI8aaGcbaGaamysaiabg2da9maalaaabaGaaGymaaqaaiaa % isdaaaGaey4kaSYaaSaaaeaacqaHapaCaeaacaaI4aaaaaaaaa!5C4E! \begin{array}{l} I = \frac{1}{2}\left( {1 + x} \right)\sin 2x\left| \begin{array}{l} \frac{\pi }{4}\\ 0 \end{array} \right. - \frac{1}{2}\int\limits_0^{\frac{\pi }{4}} {\sin 2x{\rm{d}}x} \\ I = \frac{1}{4} + \frac{\pi }{8} \end{array}\)
Vậy a = 4, b = 8 . Nên a.b = 32