jika sin A = 12/13, A terletaj di kuadran ll, tentukan nilai cos A

Sin A = 12/ 13
12 = depan
13 = miring

Cos A = samping/ miring

Samping = akar 13^2 - 12^2
= akar 169 - 144
= akar 25
= 5

Cos kuadran 2 = negatif sehingga
Cos A = samping/ miring
= -5/13

Mapel : Matematika
Kelas : X SMA
Bab : Trigonometri

Pembahasan :
Berdasarkan Identitas Trigonometri
Sin² A + Cos² A = 1
Cos A = √[1 - (Sin A)²]
Cos A = √[1 - (12/13)²]
Cos A = √[1 - 144/169]
Cos A = √25/169
Cos A = 5/13

Karena Cos dikuadran II NEGATIF, maka :
Cos A = - 5/13