It's all on the circle

Geometry Level 2

Given that $a,b,c$ and $d$ are 4 distinct non-zero real numbers such that the points $\left(a,\dfrac{1}{a}\right)$ , $\left(b,\dfrac{1}{b}\right)$ , $\left(c,\dfrac{1}{c}\right)$ and $\left(d,\dfrac{1}{d}\right)$ lie on a circle.

Find the value of $a\times b\times c\times d$ .