向量的坐标运算

题目

向量的坐标运算
已知m=(1,0),n=(1/2,(√3)/2 ),a=m+2n,b=2m-3n.,则a与b的夹角为

答案

a = m + 2n = (1, 0) + 2(1/2, √3/2) = (2, √3)b = 2m - 3n = 2(1, 0) - 3(1/2, √3/2) = (1/2, -3√3/2)cos = (a • b)/(∣a∣∣b∣) = [2*(1/2) + √3*(-3√3/2)] / { [√(2²...