Question

数学解三角形和向量结合的一道大题

Answer 1

大题我来给你做：

1

f(x)=a·b=(sinx/2,sqrt(3)cosx/2)·(cosx/2,cosx/2)=(1/2)sinx+(sqrt(3)/2)cosx+sqrt(3)/2

=sin(x+π/3)+sqrt(3)/2,f(x)=0,则：sin(x+π/3)=-sqrt(3)/2,即：x+π/3=2kπ-π/3或

x+π/3=2kπ-2π/3,即：x=2kπ-2π/3或x=2kπ-π,在[0,2π]上,x=π,x=4π/3

即f(x)在[0,2π]上的零点为π和4π/3

2

f(A)=sqrt(3),即：sin(A+π/3)=sqrt(3)/2,A是内角,则：0