The locus of the moving point whose coordinates are given by et+e−t,et−e−t where t is a parameter, is
xy=1
x+y=2
x2−y2=4
x2−y2=2
Let et+e−t,et−e−t≡(h,k) or h=et+e−t and k=et−e−t
Squaring and subtracting, we get
h2−k2=et+e−t2−et−e−t2=4
Therefore, the locus of h,k is x2−y2=4 .