在△ABC中,角A,B,C所对的边分别是a,b,c,sinC/2=64. (1)求sinC; (2)若c=2,sinB=2sinA,求△ABC的面积.
问题描述:
在△ABC中,角A,B,C所对的边分别是a,b,c,sin
=C 2
.
6
4
(1)求sinC;
(2)若c=2,sinB=2sinA,求△ABC的面积.
答
(1)由题意,cos
=C 2
,∴sinC=2×
10
4
×
6
4
=
10
4
15
4
(2)由sinB=2sinA可知b=2a,又22=a2+b2-2abcosC,∴a=1,b=2,∴S=
×1×2×1 2
=
15
4
15
4