Tanpamenggunakan tabel dan kolkulator hitung lahCos 195

cos 195
= cos (180+15)
= - cos 15
= - cos (45-30)
= - [cos 45 cos 30 + sin 45 sin 30]
= - [ ½√2 × ½√3 + ½√2 × ½]
= - ( ¼√6 + ¼√2)
= - ¼ (√6 + √2)