As shown in the figure, take the three sides of RT △ ABC as the sides and make three equilateral triangles outwards. Their areas are represented by S1, S2 and S3 respectively. Please guess the quantitative relationship between S1, S2 and S3 and explain the reason

As shown in the figure, take the three sides of RT △ ABC as the sides and make three equilateral triangles outwards. Their areas are represented by S1, S2 and S3 respectively. Please guess the quantitative relationship between S1, S2 and S3 and explain the reason

S1 + S2 = S3, the reason is as follows: ∵ as shown in the figure, take the three sides of RT △ ABC as the sides to make three squares outwards, ∵ S3 = C2, S2 = A2, S1 = B2 (8 points) and ∵ △ ABC is a right triangle, ∵ A2 + B2 = C2, ∵ S1 + S2 = S3