Using the cosine rule, we have
p2=q2+r2−2qrcosPp^{2} = q^{2} + r^{2} - 2qr \cos Pp2=q2+r2−2qrcosP
p2=82+62−2(8)(6)(112)p^{2} = 8^{2} + 6^{2} - 2(8)(6)\left(\frac{1}{12}\right)p2=82+62−2(8)(6)(121)
= 64+36−864 + 36 - 864+36−8
p2=92∴p=92 cmp^{2} = 92 \therefore p = \sqrt{92} \text{ cm}p2=92∴p=92 cm
