sinc cosa+sinc cosb = cocCsinA+cosCsinB

sinc cosa-cocCsinA = cosCsinB-sinc cosa

sin(C-A)=sin(B-C)

C-A=B-C or c-a = c-b.

2C=A+B= 180 degrees -C, then C=60 degrees.

Sin(B-A)=cosC= 1/2, B-A=30 degrees.

A=45 degrees, B=75 degrees, C=60 degrees.

Or A=B

sin(B-A)=cosC=0

C=90 degrees

Because of the existence of tanC, c

A=B can't hold on, give up

(2)acsinB/2=3+√3

ac=4√6