The first question, sinA:sinB:sinC=a:b:c from sine theorem, so according to the meaning of the question, a:b:c= 1:2:3,

Secondly, from the sum of the angles in the triangle 180 degrees and A+C=2B, we can get B=60 degrees, and from a:sinA=b:sinB, we can get sinA= 1/2, so a is 30 degrees, c is 90 degrees, and sinc =/kloc-.

3. It is proved that when a/sinA=2R on the circumscribed circle of triangle ABC, the diameter BM can pass through point B, and the angle A= angle M is obtained from the theorem of circumferential angle, and then sine is defined, so a/sinA=2R, as well as b/sinb = 2r and c/sinc =