diketahui sin α = √7/4. jika α berada di kuadran II,maka nilai cos α = ..

Mapel : Matematika
Kelas : X SMA
Bab : Trigonometri

Pembahasan :
Sin A = (√7)/4

Depan = √7
Miring = 4
Samping = - 3 (Pythagoras)

Maka....
Cos A = Samping/Miring
Cos A = -3/4

sin a = [tex] \frac{depan}{miring} [/tex]
sin a =[tex]\frac{ \sqrt{7} }{4} [/tex]
depan = [tex] \sqrt{7} [/tex]
miring = 4

[tex] samping^{2} [/tex] = [tex]miring ^{2} - depan^{2} [/tex]
[tex] samping^{2} [/tex] = [tex]4^{2} - \sqrt{7}^{2} [/tex]
[tex] samping^{2} [/tex] = 16 - 7
[tex] samping^{2} [/tex] = 9
samping = [tex] \sqrt{9} [/tex]
samping = 3

cos a = [tex] \frac{samping}{miring} [/tex]
cos a = [tex] \frac{3}{4} [/tex]
karena di kuadran II, maka :
cos a = -[tex] \frac{3}{4} [/tex]