20 1 1 How to do the 25th question of Ningbo Mathematics Test Paper? It is urgent.

The first question is the real question.

Second question, is there a problem, a? +b？ =c？ And because △ABC is a singular triangle and b > a.

So c? +a？ =2b？

So 2a? =b？

So a: b: c = 1: √ 2: √ 3.

The third question: ① Because AB is the diameter of a circle.

So AC? +BC？ =AB？

AD？ +BD？ =AB？

It is also known from the question that d is the midpoint of a semicircle.

So AD=BD

So AC? +BC？ =2AD？

Because BC=CE, AD=AE.

So AC? +CE？ =2AE？

So △ACE is a singular triangle.

② If △ACE is a right triangle.

So AC? +AE？ =CE？ Or CE? +AE？ =AC？

According to the second question,

Ac: AE: ce = 1: √ 2: √ 3 or ce: AE: AC = 1: √ 2: √ 3.

So AC: CB = 1: √ 3 or √ 3: 1.

So ∠AOC=60? Or 120?