双曲线上一点到两焦点的斜率之积 如何推导?答:设双曲线方程为x^2/a^2-y^2/b^2=1(a>0,b>0),其顶点为A1(-a,0),A2(a,0),P(asect,btant)在双曲线上,PA1的斜率k1=btant/(asect+a),PA2的斜率k2=btant/(asect-a),k1k2=(btant)^2/[(asect)^2-a^2]=b^2/a^2,OP的斜率=btant/(asect)
曲线上一点法向量的斜率怎么表示答:设双曲线方程为x^2/a^2-y^2/b^2=1(a>0,b>0), 其顶点为A1(-a,0),A2(a,0), P(asect,btant)在双曲线上, PA1的斜率k1=btant/(asect+a), PA2的斜率k2=btant/(asect-a), k1k2=(btant)^2/[(asect)^2-a^2] =b^2/a^2, OP的斜率=btant/(asect)向量...