Question

most important questions​

Answer 1

Answer:

let a triangle a=9 c=12

by pythagoras theorem b=15

Now in Triangle ABC,

use cosine rule

$cos \: c = \frac{a {}^{2} + {b}^{2} - {c}^{2} }{2ab} \\ = \frac{81 + 225 - 144}{2 \times 9 \times 15} \\ = \frac{162}{2 \times 9 \times 15} = \frac{9}{15} = \frac{3}{5}$