take the square root of d^2 [(ht+hr)^2 / d^2 + 1], this whole term is underneath a square root...
(d^2 [(ht+hr)^2 / d^2 + 1])^1/2 = d [(ht+hr)^2 / d^2 + 1]^1/2
take the square root of d^2 [(ht+hr)^2 / d^2 + 1], this whole term is underneath a square root...
(d^2 [(ht+hr)^2 / d^2 + 1])^1/2 = d [(ht+hr)^2 / d^2 + 1]^1/2