java - 求余弦角! vector 产品

Question

我正在寻找余弦α角的答案。

cos(alpha)=RT(vector).R(vector)/(modulus)RT(vector).(modulus)R(vector)

那么我应该需要找到角度 alpha。

public double dot1(double[] vectorA, double[] vectorB){
        double[] vecPro;
        vecPro = new double[2];
        vecPro[0] = vectorA[0]*vectorB[0];
        vecPro[1] = vectorA[1]*vectorB[1];
        return 0;
    }

这段代码只是我到目前为止所做的一个示例!为RT( vector ).R( vector )的点积。嗯，我的做法是正确的，因为我是 java 语言的新手。

Answer 1

这不计算点积。 This does

public double dot1(double[] vectorA, double[] vectorB){ //if they're from R^2
        double[] vecPro = new double[2];
        vecPro[0] = vectorA[0]*vectorB[0];
        vecPro[1] = vectorA[1]*vectorB[1]; 
        //you did fine up to here
        //But, you should return the result (sum of components products) @see wiki link
        //0 surely isn't the result you want for two arbitrary vectors
        return vecPro[0] + vecPro[1]; 
}