Since we've correctly calculated the area two different ways, they have to be the same number, and that's why the squares of one, one, two, three, five and eight add up to eight times 13.
面積を２種類の方法で 計算できました 結果はお互いに同じなので 1 1 2 3 5 8 の平方数を足すと 8 x 13 になると言えるのです