## Elementary Geometry for College Students (6th Edition)

$8^{2}$ = $(6)^{2}$ + $(9)^{2}$ - 2*6*9*cos β
Given data a=6,b =8, c=9 Using theorem 11.4.3 In triangle ABC $b^{2}$ = $a^{2}$ + $c^{2}$ - 2ac cos β $8^{2}$ = $(6)^{2}$ + $(9)^{2}$ - 2*6*9*cos β