Here is another question of continued fraction which I got stuck with.

Question : a_0 might be 0, but a_1 cannot be 0

a_n for positive n must be strictly positive, but a_0 may be zero. Construct an example(i.e. specific a_n for which a_0 = 0 ). Explain the geometric significance of what you've done.

Please teach me how to solve it. Thank you very much.