If $\displaystyle a:b:c=7:8:9 $ ,
find $\displaystyle \cos A:\cos B:\cos C $
where a,b,c are the sides opposite to angles A,B,C in triangle ABC.
please help me...
1. I assume that the a in cos(a) denotes the angle opposite the side a. To avoid some confusion I'll use $\displaystyle \alpha$ to denote this angle. Consequently $\displaystyle \beta, \gamma$ denote the angles opposite the sides b or c.
2. Use a triangle with the side lengthes
a = 7, b = 8, c = 9
3. Use the Cosine rule to determine the cosine values of the corresponding angles.
I've got:
$\displaystyle \cos(\alpha) : \cos(\beta) : \cos(\gamma) = 14 : 11 : 6$