We introduce a sequence of Fibonacci right-angled triangles associated
with a generalized Fibonacci sequence and prove, for a given positive integer k,
there exist a generalized Fibonacci sequence fn such that ®2n = ®2n+1 + ®2n+2
holds for the angles ®n defined by tan ®n = k=fn, 0 < ®n < ¼=2. By considering
the Pell’s type equation x2 ¡ 5y2 = §4k2, we also determine all the solutions to
®2n = ®2n+1 + ®2n+2 by generalized Fibonacci sequences.