Question

在三角形ABC中,若b=1,c=根号3,角c=2派除以3,则a为多少?

Answer 1

c^2=a^2+b^2-2abcos(2π/3)

3=a^2+1-2a*1*(-1/2)=a^2+1+a

a^2+a-2=0

(a+2)(a-1)=0

a=-2舍去,a=1