Question

高中数学,急!在△ABC中,已知角A,B,C所对的边分别为a,b,c,直线L1:cx+y+1=0与直线L2:(a^2+b

Answer 1

(1)-c=(a^2+b^2-3/2ab)/(-c)

c^2=a^2+b^2-3/2ab

a^2+b^2-c^2=3/2ab

cosC=(a^2+b^2-c^2)/2ab=3/4

(2)sinC=(√7)/4

c^2=a^2+b^2-3/2ab>2ab-3/2ab=1/2ab

a