已知平面上3个向量a,b,c 的模均为1. 它们相互间夹角为120度。 求证（a-b)垂直于c
\u5df2\u77e5\u5e73\u9762\u4e0a\u4e09\u4e2a\u5411\u91cfa\uff0cb\uff0cc\u7684\u6a21\u90fd\u4e3a1\uff0c\u4ed6\u4eec\u76f8\u4e92\u4e4b\u95f4\u7684\u5939\u89d2\u5747\u4e3a120\uff0c\uff081\uff09\u6c42\u8bc1\uff08a\u2014b\uff09\u5782\u76f4c\u3002\u8bbe \u5411\u91cfa,b,c \u4e3a OA, OB, OC \u5219(a-b) = BA \u89d2AOB = 120\u5ea6, OA=OB=1 \u6240\u4ee5 \u89d2ABO = 30\u5ea6 \u53cd\u5411\u5ef6\u957fOC \u5230D \u89d2DOB = 60\u5ea6 \u6240\u4ee5(a-b)\u5782\u76f4c
\u8bbe \u5411\u91cfa,b,c \u4e3a OA, OB, OC
\u5219 (a-b) = BA
\u89d2AOB = 120\u5ea6, OA=OB=1
\u6240\u4ee5 \u89d2ABO = 30\u5ea6
\u53cd\u5411\u5ef6\u957fOC \u5230D
\u89d2DOB = 60\u5ea6
\u6240\u4ee5(a-b)\u5782\u76f4c
（a-b)*c=ac-bc~~~~~~~向量具有分配律
=|a||c|cos120-|b||c|cos120 ~~~向量相乘等于两个向量模的乘积再乘以他们之间的夹角
=0
(a-b)*c = |a-b| * |c| *cos A，其中|a-b|是向量a-b的模，不为零（因为a和b有夹角），A是向量a-b与c的夹角。因为(a-b)*c=0，所以A必定为90°或者270°，表明向量a-b垂直于向量c。
abc的模都是1
所以abc的绝对值符号相等（模就是绝对值符号，叫距离）
Zhuzhou
Red Net News, March 14 (correspondent Tande Hui) CMB owners reversing dumbfound the disputes of others,newport cigarettes sales, had a sorry understanding can be obtained. However, the owner not only failed to apologize, but gave the driver deliberately drove escape. The face of the masses catch up, he not only did not stop, and driving crashed into two people to catch up. One person injured in the post, and malicious run over their body, causing instant death. March 13, Liling City Procuratorate owners Xiaomou suspicion of manslaughter, submitted to Zhuzhou City Procuratorate for prosecution.
2008 年 12 月 11 morning, blessing God who lives in Town, Liling City, Ridge neighborhood Xiaomou Changsha, Hunan B63022 driving bus for the grades in the blessing of God on the streets of town when reversing, just case of a motorcycle passing by the local villagers Tangmou,cheap monster beats, soup aware of the danger after the emergency brakes,monster beats outlets, car carrying the man fell to the ground. After the fall, Tom see Xiaomou on their own were not ignored, heart anger, Shaw stopped the bus immediately. Fighting this dispute and both sides were open, to persuade the people around, regardless of the car in front Tangmou Xiaomou and others blocked, forcing motorists to Tangmou injured fled the scene.
soup being near the scene of the accident and the motorcycle taxi driver brother Zhou, the text of a car, who immediately rushed to catch up. God Ma ridge road double-plate section, Tom's brother over Xiaomou bus driver, will be placed across the middle of the road motorcycle,cheap newport cigarettes, their own standing on the road on the left indicate Xiaomou parking. See someone out of the way, Shaw not only did not stop, but too hard to hit the steering wheel to the soup brother. Xianshibumiao brother Tom, quickly dodge roadside tree, the Xiaomou see the impact is invalid, a step on the gas to escape forward.
At this point, behind the week, they take the paper arrived with a motorcycle than driving under the Pakistan Xiaomou escape, and in front of about six or seven meters on the right side the road to stop, then get off to a street culture. See the path is blocked, in front of someone knowing Xiaomou case, still ignoring the safety of others, to accelerate the motorcycle collision, resulting in bus front and rear motorcycle collided violently, Zhou remained in the car with people hit with a car on the spot to fly a few meters away the middle of the road. After Xiaomou not only failed to stop, but accelerated and fled the scene. In the escape process, Xiaomou drive again from the Zhou who deliberately run over, resulting in the week died on the spot.
by forensic examination: the deceased Zhou Department of brachiocephalic, left subclavian artery, left common carotid artery rupture caused by hemorrhagic shock and death.
is the source: Red Net Author: Tan Dehui
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