Jawabanmu

2014-05-17T11:27:58+07:00
A² = b² + c² - 2bc.cosA
cos A = 0
jadi sin A = 1
1 4 1
2014-05-17T17:24:26+07:00
Cos A=(b^2+c^2-a^2)/2.b.c
=(3+4-7)/2.akar3.2
=0
cos yg brnilai 0 adlh 90°
mka sin A=sin90=1
1 4 1