Ini rumus nya gimana yaa. Yang bisa bantu dong

Bangun Datar


Nmr 5
L∆ ABC = ½.AB×AC.SinA
24√3 = ½.12×8.SinA
24√3 = 48.SinA
½√3 = SinA
Sin60° = SinA
maka,
CosA = Cos60° = ½

Nmr6
S = ½(2+3+4) = 4,5
..
L = √4,5(4,5-2)(4,5-3)(4,5-4)
= √4,5(2,5)(1,5)(0,5)
= √8,4375
= 2,9 cm² atau bulatkan saja 3cm²

Maaf jika salah..

NOMOR 5
L = 1/2 . AB . AC . sin A
24√3 = 1/2 . 12.8 sin A
24 √3 = 48 sin A
sin A = 24√3/48
sin A = 1/2 . √3
A = 60˚

maka :
cos A
= cos 60˚
= 1/2

NOMOR 6
L = √{s(s-a)(s-b)(s-c)}
L = √{4,5(4,5-2)(4,5-3)(4,5-4)}
L = √( 4,5 x 2,5 x 1,5 x 0,5)
L = √ 8,4375
L = 2,9 satuan