Explanation

With 0 < x < 90 degrees, tan x = 1 gives x = 45 degrees. By the double-angle formula, 2 sin x cos x = sin 2x = sin 90 degrees = 1. Equivalently, sin 45 = cos 45 = 1/sqrt(2), so 2*(1/sqrt(2))*(1/sqrt(2)) = 1. Hence the value is 1, option (b).