Mohon bantuannya yaa, terima kasih <3

<p>diket: panjang BC = 15 cm</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;∠AOD = 60°</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;berarti ∠COD = 60° sehingga ∠DCO = 30° dan ∠DCB = 60°</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; panjang DC</p><p>cos 60° = ---------------</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; panjang BC</p><p>1 &nbsp; &nbsp; &nbsp; panjang DC</p><p>-- &nbsp;= ----------------</p><p>2 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;15</p><p>panjang DC = 7,5 cm</p><p>&nbsp;</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; panjang DC</p><p>cos 30° = &nbsp; -----------------</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; panjang OC</p><p>1 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;7,5</p><p>-- √3 &nbsp;= &nbsp;----------------</p><p>2 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;panjang OC</p><p>panjang OC = 5√3 cm</p><p>&nbsp;</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; panjang BD</p><p>sin 60° = &nbsp;---------------</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; panjang BC</p><p>1 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; panjang BD</p><p>-- √3 &nbsp;= &nbsp;----------------</p><p>2 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;15</p><p>panjang BD = 7,5√3 cm</p><p>&nbsp;</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; panjang OD</p><p>sin 30° = ----------------</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; panjang OC</p><p>1 &nbsp; &nbsp; &nbsp; panjang OD</p><p>-- &nbsp;= ----------------</p><p>2 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;5√3</p><p>panjang OD = 2,5√3 cm</p><p>panjang OB = 2,5√3 + 7,5√3 = 10√3 cm</p><p>&nbsp;</p><p>Kll OABC = panjang OA + panjang AB + panjang BC + panjang CO</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;= &nbsp;5√3 + 15 + 15 + 5√3</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;= 40√3 cm</p><p>&nbsp;</p><p>panjang OB = 7,5 + 7,5 = 15 cm</p><p>Jawabannya pilihan E</p><p>semoga membantu.</p>