(选择题)在三角形ABC中,C=2B,那么sin3B/sinB=?A a/b B b/a C a/c D c/a
问题描述:
(选择题)在三角形ABC中,C=2B,那么sin3B/sinB=?A a/b B b/a C a/c D c/a
答
C=2B
A=π-C-B=π-3B
sinA=sin(π-3B)=sin3B
sin3B/sinB
=sinA/sinB
=a/b