The tangent to the hyperbola xy=c2 at point P(t) intersects the X-axis at T and the Y-axis at T′ . The normal to the hyperbola at P(t) intersects the X-axis at N and the Y-axis at N′ . The areas of the triangles PNT and PN′T′ are Δ and Δ′ respectively, then Δ1+Δ′1 is
(1) equal to 1
(2) depends on t
(3) depends on c
(4) equal to 2