Verify that parallelogram ABCD with vertices A(-5,-1), B(-9,6), C(-1,5), and D(3,-2) is a rhombus by showing that it is a parallelogram with perpendicular diagonals.

Answer 1

AB and CD have slope -7/4
BC and AD have slope -1/8
AC has slope 3/2 and BD has slope -2/3
all four sides have length √65