From a226e0086dda0efc70fa1a9ddf129a9bc832218a Mon Sep 17 00:00:00 2001 From: "weiye.wang" Date: Sun, 21 Jan 2024 13:46:18 +0800 Subject: [PATCH] =?UTF-8?q?=E4=BF=AE=E6=94=B918513=E9=A2=98=E9=9D=A2?= =?UTF-8?q?=E5=92=8C=E7=AD=94=E6=A1=88?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- 题库0.3/Problems.json | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/题库0.3/Problems.json b/题库0.3/Problems.json index 3c11d779..393a523d 100644 --- a/题库0.3/Problems.json +++ b/题库0.3/Problems.json @@ -497544,19 +497544,20 @@ }, "018513": { "id": "018513", - "content": "在$\\triangle ABC$中, 设$\\overrightarrow{CA}=\\overrightarrow {a}, \\overrightarrow{CB}=\\overrightarrow {b}$, 记$\\triangle ABC$的面积为$S$\n(1) 求证: $S=\\dfrac{1}{2} \\sqrt{|\\overrightarrow {a}|^2|\\overrightarrow {b}|^2-(\\overrightarrow {a} \\cdot \\overrightarrow {b})^2}$;\n(2)设$\\overrightarrow {a}=(x_1, y_1), \\overrightarrow {b}=(x_2, y_2)$, 求证: $S=\\dfrac{1}{2}|x_1 y_2-x_2 y_1|$.\n$\\overrightarrow{OC} \\perp$. 设$OA$、$B$、$C$是平面上四点, 已知$\\overrightarrow{OA} \\perp \\overrightarrow{BC}, \\overrightarrow{OB} \\perp \\overrightarrow{AC}$. 求证:", + "content": "在$\\triangle ABC$中, 设$\\overrightarrow{CA}=\\overrightarrow {a}, \\overrightarrow{CB}=\\overrightarrow {b}$, 记$\\triangle ABC$的面积为$S$.\\\\\n(1) 求证: $S=\\dfrac{1}{2} \\sqrt{|\\overrightarrow {a}|^2|\\overrightarrow {b}|^2-(\\overrightarrow {a} \\cdot \\overrightarrow {b})^2}$;\\\\\n(2) 设$\\overrightarrow {a}=(x_1, y_1), \\overrightarrow {b}=(x_2, y_2)$, 求证: $S=\\dfrac{1}{2}|x_1 y_2-x_2 y_1|$.", "objs": [], "tags": [ "第五单元" ], "genre": "解答题", - "ans": "", + "ans": "证明略; 证明略", "solution": "", "duration": -1, "usages": [], "origin": "空中课堂必修第二册平面向量例题与习题", "edit": [ - "20230705\t王伟叶" + "20230705\t王伟叶", + "20240121\t王伟叶" ], "same": [], "related": [],