( 1)

Using sine theorem

sinA=b/sinB

∫∠B = 2∠A，

Then a/sinA=b/sin2A.

That is, b/a=sin2A/sinA=2cosA.

∴2 Xhosa =2√6/3

∴ Kossa =√6/3

(2)

Using cosine theorem

Answer? =b？ +c？ -2bc*cosA

Substitute a = 3 and b = 2 √ 6.

∴ 9=24+c？ -4√6*(√6/3) degrees Celsius

∴ c？ -8c+ 15=0

∴ (c-3)(c-5)=0

∴ c=3 or c=5

When c=3, C=A, then B=2A, then this triangle is an isosceles right triangle. If it is not satisfied, give up.

∴ c=5