According to Pythagorean Theorem A? +a？ =b？ When a= 1 and b= root number two, the known edge data is directly brought into the calculation when doing the problem.

In a right-angled triangle of 30 60 90, let the right-angled side of 30 be A, the hypotenuse be B and the other right-angled side be C.

∵Rt△ The right angle side opposite to the 30 angle is half of the hypotenuse.

∴2a=b

According to Pythagorean Theorem A? +c？ =4a？ When a= 1, b=2 c= root number three.