diketahui segitiga abc a=2√7 b=4 c=6 tentukan sin a

berdasarkan aturan cosinus
a^2 = b^2 + c^2 - 2bc cos A
(2V7)^2 = (4)^2 + (6)^2 - 2.4.6 cos A
28 = 16 + 36 - 48 cos A
28 = 52 - 48 cos A
48 cos A = 52 - 28
48 cos A = 24
cos A = 24/48
cos A = 1/2
A = 60°
sin A = sin 60° = 1/2V3