pada segitiga ABC jika panjang AB : 7cm, BC : 9cm dan AC : 6cm, hitunglah sidut A,B dan C

misal BC=a
AC=b
AB=c
menggunakan aturan cosinus :
[tex] \cos(a) = \frac{ {6}^{2} + {7}^{2} - {9 {}^{2} } }{2 \times 6 \times 7 } \\ \cos(a) = \frac{1}{21} \\ a = 87.27[/tex]
menggunakan aturan sinus :
[tex] \frac{a}{ \sin(a) } = \frac{b}{ \sin(b) } \\ \frac{9}{ \sin(87.27) } = \frac{6}{ \sin(b) } \\ \sin(b) = \frac{6 \sin(87.27) }{9} \\ \sin(b) = 0.66591 \\ b = 41.75 [/tex]
[tex]c = 180 -(a + b) \\ c = 180 - (87.27 + 41.75) \\ c = 180 - 129.02 \\ c = 51.98[/tex]
A=87.27
B=41.75
C=51.98