As shown in the figure, in RT △ ABC, ∠ C = RT ∠, three semicircles are made by taking the three sides of the right triangle as the diameter, then the relationship among S1, S2 and S3 is as follows:______ .

As shown in the figure, in RT △ ABC, ∠ C = RT ∠, three semicircles are made by taking the three sides of the right triangle as the diameter, then the relationship among S1, S2 and S3 is as follows:______ .

So the answer is: S2 + S3 = S1