Trong không gian Oxyz, cho hai đường thẳng \(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeuiLdq0aaS % baaSqaaiaaigdaaeqaaOGaaiOoamaalaaabaGaamiEaiabgkHiTiaa % igdaaeaacqGHsislcaaIYaaaaiabg2da9maalaaabaGaamyEaiabgU % caRiaaikdaaeaacaaIXaaaaiabg2da9maalaaabaGaamOEaiabgkHi % TiaaiodaaeaacaaIYaaaaaaa!464F! {\Delta _1}:\frac{{x - 1}}{{ - 2}} = \frac{{y + 2}}{1} = \frac{{z - 3}}{2}\) và \(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeuiLdq0aaS % baaSqaaiaaikdaaeqaaOGaaiOoamaalaaabaGaamiEaiabgUcaRiaa % iodaaeaacaaIXaaaaiabg2da9maalaaabaGaamyEaiabgkHiTiaaig % daaeaacaaIXaaaaiabg2da9maalaaabaGaamOEaiabgUcaRiaaikda % aeaacqGHsislcaaI0aaaaaaa!4646! {\Delta _2}:\frac{{x + 3}}{1} = \frac{{y - 1}}{1} = \frac{{z + 2}}{{ - 4}}\). Góc giữa hai đường thẳng \(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeuiLdq0aaS % baaSqaaiaaigdaaeqaaOGaaiilaiabfs5aenaaBaaaleaacaaIYaaa % beaaaaa!3B49! {\Delta _1},{\Delta _2}\) bằng:
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Lời giải:
Báo saiTa có: \(\Delta_1\) có VTCP là:\(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaa8Haaeaaca % WG1bWaaSbaaSqaaiaaigdaaeqaaaGccaGLxdcacqGH9aqpdaqadaqa % aiabgkHiTiaaikdacaGG7aGaaGymaiaacUdacaaIYaaacaGLOaGaay % zkaaaaaa!40C0!$ \overrightarrow {{u_1}} = \left( { - 2;1;2} \right)\) , \(\Delta_2\) có VTCP là:\(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaa8Haaeaaca % WG1bWaaSbaaSqaaiaaikdaaeqaaaGccaGLxdcacqGH9aqpdaqadaqa % aiaaigdacaGG7aGaaGymaiaacUdacqGHsislcaaI0aaacaGLOaGaay % zkaaaaaa!40C2! \overrightarrow {{u_2}} = \left( {1;1; - 4} \right)\)
Gọi \(\alpha\) là góc giữa hai đường thẳng \(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeuiLdq0aaS % baaSqaaiaaigdaaeqaaOGaaiilaiabfs5aenaaBaaaleaacaaIYaaa % beaaaaa!3B49! {\Delta _1},{\Delta _2}\) ta có:
\(% MathType!MTEF!2!1!+- % feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaci4yaiaac+ % gacaGGZbGaeqySdeMaeyypa0ZaaSaaaeaadaabdaqaamaaFiaabaGa % amyDamaaBaaaleaacaaIXaaabeaaaOGaay51GaGaaiOlamaaFiaaba % GaamyDamaaBaaaleaacaaIYaaabeaaaOGaay51GaaacaGLhWUaayjc % SdaabaWaaqWaaeaadaWhcaqaaiaadwhadaWgaaWcbaGaaGymaaqaba % aakiaawEniaaGaay5bSlaawIa7aiaac6cadaabdaqaamaaFiaabaGa % amyDamaaBaaaleaacaaIYaaabeaaaOGaay51GaaacaGLhWUaayjcSd % aaaiabg2da9maalaaabaWaaqWaaeaacqGHsislcaaIYaGaaiOlaiaa % igdacqGHRaWkcaaIXaGaaiOlaiaaigdacqGHRaWkcaaIYaGaaiOlam % aabmaabaGaeyOeI0IaaGinaaGaayjkaiaawMcaaaGaay5bSlaawIa7 % aaqaamaakaaabaWaaeWaaeaacqGHsislcaaIYaaacaGLOaGaayzkaa % WaaWbaaSqabeaacaaIYaaaaOGaey4kaSIaaGymaiabgUcaRiaaikda % daahaaWcbeqaaiaaikdaaaaabeaakiaac6cadaGcaaqaaiaaigdacq % GHRaWkcaaIXaGaey4kaSYaaeWaaeaacqGHsislcaaI0aaacaGLOaGa % ayzkaaWaaWbaaSqabeaacaaIYaaaaaqabaaaaOGaeyypa0ZaaSaaae % aacaaI5aaabaGaaG4maiaac6cacaaIZaWaaOaaaeaacaaIYaaaleqa % aaaakiabg2da9maalaaabaWaaOaaaeaacaaIYaaaleqaaaGcbaGaaG % Omaaaaaaa!7CBE! \cos \alpha = \frac{{\left| {\overrightarrow {{u_1}} .\overrightarrow {{u_2}} } \right|}}{{\left| {\overrightarrow {{u_1}} } \right|.\left| {\overrightarrow {{u_2}} } \right|}} = \frac{{\left| { - 2.1 + 1.1 + 2.\left( { - 4} \right)} \right|}}{{\sqrt {{{\left( { - 2} \right)}^2} + 1 + {2^2}} .\sqrt {1 + 1 + {{\left( { - 4} \right)}^2}} }} = \frac{9}{{3.3\sqrt 2 }} = \frac{{\sqrt 2 }}{2}\)
\(% MathType!MTEF!2!1!+- % feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeyO0H4Taeq % ySdeMaeyypa0JaaGinaiaaiwdadaahaaWcbeqaaiaaicdaaaaaaa!3D5A! \Rightarrow \alpha = {45^0}\)
Đề thi thử tốt nghiệp THPT QG môn Toán năm 2020
Tuyển chọn số 4