Question

已知三角形ABC的三个顶点的直角坐标系分别为A(3,4),B(0,0),C(c,0),若AB*AC=0,求c的值

Answer 1

AB=B-A=(0-3,0-4)=(-3,-4)

AC=C-A=(c-3,0-4)=(c-3,-4)

AB*AC

=-3(c-3)+(-4)*(-4)=0

-3c+9+16=0

3c=25

c=25/3