Minggu, 22 Agustus 2010

TUGAS KELAS XII IPS DEADLINE 24 AGUSTUS 2010

Bagi siswa kelas XII IPS silahkan kerjakan tugas ini di buku tugas dan silahkan dikumpulkan tanggal 24 Agustus 2010. Klik di sini

Rabu, 18 Agustus 2010

cos 10 + cos 110 + cos 130

do you know what is the value of cos 10 + cos 110 + cos 130? 
according to mathematical calculations if it is equal to zero, how can you?explanation like this:The first time you have to remember that the sum of the commutative law applies, so nothing wrong if we do first is to calculate the value of cos 110 + cos 130 first.
(Remember that: cos (A + B) + cos (A - B) = 2.cos A.cos B) 
The value of cos 110 + cos 130 = 2.cos 120.cos10
                                   
= 2. (-0.5). Cos 10
                                   
= - Cos 10    

 from about cos 10 + cos 110 + cos 130 = cos 10 - cos 10
                                                              
= 0

became evident that the cos 10 + cos 110 + cos 130 = 0 
thanks please write your comment