请问:杨辉三角除了上两个相加等于下面一个,还有什么规律?就是说比如我写(A+B)...
简单的说一下就是两个未知数和的幂次方运算后的系数问题,比如(x+y)的平方=x的平方+2xy+y的平方,这样系数就是1,2,1这就是杨辉三角的其中一行,立方,四次方,运算的结果看...
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这件针织衫里面搭配白色衬衫好看来自还是蓝色衬衫好看,裤子陪蓝色牛仔裤还是卡其休闲裤呢?以女生的眼光,哪一个更好看一些呢? A:(藏青色针织衫+蓝色牛仔裤) B:(白衬衫)C:(蓝衬衫+卡其休闲裤),360问答就是A+B和A+C哪一个好看机?
白衬衫+藏青色针织衫,浅黄色哈伦裤
在△ABC中,三个内角A,B,C的对边分别为a,b,c,其中c=2,且cosAcosB=ba=31.(1)求证:△ABC是改直角
(1)由正弦定理得:asinA=bsinB得:ba=sinBsinA,又cosAc前代osB=ba,∴cosAcosB=sinBsinA,整理为sinAcosA=sinBcosB...
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